Download Grade 7 Life Posttest

Grade 7 Life Posttest
Select the best answer to each question.
____
1. Jacob was studying a timeline that represented the history of life. His assignment was to use logic to interpret
the patterns he saw there. The timeline showed that during a period of time called the Cambrian period, many
new species of multicellular animals suddenly appeared in the fossil record. Some of the multicellular animals
that appeared in the fossil record before the Cambrian period shared similar traits with some of the new
species that appeared in the fossil record during the Cambrian period. Which statement is a logical
interpretation of these facts?
A. The species that lived in the Cambrian period are still living today.
B. The species that lived in the Cambrian period were ancestors of the species that lived prior
to that period.
C. The species that lived in the Cambrian period could have descended from the species that
lived prior to that period.
D. The species that lived in the Cambrian period were unrelated to the species that lived prior
to that period.
____
2. Luis was collecting fossilized shark teeth at a field site. After working for hours to carefully excavate fossils
from a certain layer of rock, he found several teeth that had 12 tiny points along each edge. In a newer layer
of rock that was located closer to the surface, he had found similar shark teeth, but each of these teeth had 24
tiny points along each edge. What evidence could Luis consider to answer the question of which species of
shark had lived more recently than the other?
A. Fossils found in a certain field site are all from the same period of time.
B. Fossils found in the same type of rock are always from a certain time period.
C. Fossils found in deeper layers of rock are usually from organisms that lived further in the
past than organisms found in more shallow layers of rock.
D. Fossils found in deeper layers of rock are usually from organisms that lived in the more
recently than organisms found in more shallow layers of rock.
____
3. The branching diagram below shows hypothesized relationships between some animals that are alive today.
Christopher’s biology class is going on a field trip to a natural history museum, and each student is picking a
fossil to look for at the museum. The museum features a special collection of fossils from animals that lived
45 million years ago. What fossil from the diagram should Christopher pick if he wants to look for a specimen
of it at the museum?
A. a fossilized hippopotamus
B. a fossilized toothed whale
C. a fossilized animal that is ancestral to both the hippopotamuses and toothed whales
D. a fossilized animal that is ancestral to both baleen whales and hoofed grazing mammals
____
4. The diagram below shows the changes over time in a population of mice in the wild after a population of
hawks has moved into their environment. The white and dark mice differ only in color.
Which statement is the most likely explanation for why the mouse population changed over time?
A. The hawks eat more dark mice than white mice because the dark mice taste better.
B. The white mice are able to reproduce more successfully than the dark mice do.
C. The hawks eat more white mice than dark mice because they can see the white mice more
easily.
D. The hawks eat more dark mice than white mice, because they can see the dark mice more
easily.
____
5. Cheetahs are a species of large wild cats that live in Africa. Their populations have very low levels of genetic
variation. How could this affect a cheetah population’s ability to evolve in response to changes in their
environment, such as decreased numbers of a favorite prey?
A. When populations have low genetic diversity, they will all adapt quickly to a changing
environment.
B. When populations have low genetic diversity, they will be unable to gain variation through
mutation.
C. When populations have low genetic diversity, they have high diversity in physical traits,
and some individuals will probably find a new kind of prey to eat.
D. When populations have low genetic diversity, it is less likely that they will be able to adapt
to changed environment and find a new kind of prey to eat.
____
6. When a volcano erupted on a small island in the Pacific Ocean, the lava and ash covered much of the
surrounding forest. The birds that lived in this forest were able to fly to safer parts of the forest, but they
stayed on the island because it was too far to fly to other islands. As a result, the number of appropriate nest
sites available for birds who already lived in the remaining forest was suddenly very limited. Which birds do
you think would be most likely to survive after the volcano erupts?
A. Competition for nesting sites would be too great for any of the birds to survive.
B. Birds that establish nesting sites after the time of year when most birds establish their
nesting sites would survive.
C. Birds that establish nesting sites during the time of year when most birds establish their
nesting sites would survive.
D. Birds that establish nesting sites before the time of year when most birds establish their
nesting sites would survive.
____
7. A species of rodent lives in a moist forest climate. Over time, the climate becomes drier and more desert-like.
Which of these adaptations would most likely will improve the chances that the rodent species could survive
as its environment changes?
A.
B.
C.
D.
____
being able to eat plants that survive in the changed environment
being able to eat only one type of berry
living above ground in damp areas
having dark hair and small ears
8. Populations of lake trout in Lake Superior were in decline from overfishing and environmental pollution
when sea lampreys invaded the lake. Sea lampreys are parasites that kill lake trout. The following table shows
the approximate population sizes of each species in Lake Superior at different points in the invasion process.
Year
1940
1955
1970
1985
POPULATIONS OF LAKE TROUT AND SEA LAMPREY IN LAKE SUPERIOR
Lake Trout Population Size Sea Lamprey Population
Size
150,000
0
55,000
175,000
1,000
45,000
100,000
15,000
What are two possible explanations for the increased number of lake trout in 1985?
A. Lake trout could have adapted to the presence of sea lampreys, or people could have
begun effective conservation to protect trout.
B. Lake trout could have adapted to the presence of sea lampreys, or people could have
decided to eliminate lake trout from Lake Superior.
C. Lake trout as a species could have experienced extinction and then recovered, or sea
lamprey could have experienced extinction allowing lake trout to recover.
D. Lake trout as a species could have experienced extinction and then recovered, or sea
lamprey could have adapted to their new environment to become even deadlier parasites.
____
9. Semra was analyzing data about the loss of biodiversity in habitats in tropical rainforests due to deforestation
as people clear land. Biodiversity is a measure of the number and variety of species in a certain location at one
time. Semra was trying to clarify the relationship between the concepts of biodiversity and extinction. Which
statement most clearly defines the relationship between biodiversity and extinction?
A. As more species in a rainforest go extinct, biodiversity of the rainforest decreases.
B. As more species in a rainforest go extinct, biodiversity of the rainforest increases.
C. As more species in a rainforest go extinct, biodiversity of the rainforest stays the same.
D. The extinction of species in a rainforest does not affect the biodiversity of the rainforest.
____ 10. Delia is teaching her sister about important molecules in the body. She tells her sister that one molecule
provides a set of instructions that determines traits, such as eye color or hair color. Which molecule is Delia
describing?
A. DNA
B. glucose
C. cellulose
D. cholesterol
____ 11. Living things are made up of many different types of molecules. One type of moledule contains hereditary
information that is passed from one generation to another.
What type of molecule is shown in the illustration above?
A. carbohydrate
B. DNA
C. lipid
D. protein
____ 12. Hereditary information is passed from one generation to the next. Which two processes are responsible for the
passage of hereditary information from generation to generation in mammals, birds, reptiles, fish, and other
animals?
A.
B.
C.
D.
meiosis and fertilization
mitosis and chromosomes
DNA replication and mitosis
asexual reproduction and DNA replication
____ 13. Look at the diagram below.
Which of these statements is correct according to the diagram?
A.
B.
C.
D.
Each offspring has a 25% probability of inheriting the alleles PP.
Each offspring has a 25% probability of inheriting the alleles Pp.
Each offspring has an equal probability of inheriting the alleles PP or Pp.
Each offspring is more likely to inherit pp than any other combination of alleles.
____ 14. For a type of pea plant, round seeds (R) are dominant to wrinkled seeds (r). A pea plant with the genotype Rr
is crossed with another pea plant with the genotype Rr. What percent of the offspring are expected to have
wrinkled seeds?
A.
B.
C.
D.
100
75
50
25
____ 15. The Punnett square below shows a cross between two organisms with the genotype Aa.
What genotype should be entered in the top left box of the Punnett square?
A. aa
B. aA
C. Aa
D. AA
____ 16. Which of these statements correctly describes a difference between asexual and sexual reproduction?
A. Asexual reproduction increases genetic diversity, but sexual reproduction does not.
B. Asexual reproduction involves one parent, and sexual reproduction involves two parents.
C. Asexual reproduction increases a species’ chances of surviving unfavorable conditions,
but sexual reproduction does not.
D. The offspring produced by asexual reproduction are not identical to each other, but those
of sexual reproduction are identical to each other.
____ 17. The processes of sexual and asexual reproduction involve different types of cell division. Consider this
example: Akash clips a stem of his potted houseplant. He places the stem in a glass of water. After about two
weeks, he notices that there are several roots visible. He then plants the clipped stem in another pot, where it
continues to grow. Which process or processes of cell division are involved in the production of the new plant
from the original plant?
A.
B.
C.
D.
mitosis only
meiosis only
first mitosis, then meiosis
first meiosis, then mitosis
____ 18. Sperm and eggs are involved in the reproduction of many organisms. Which process produces sperm and
eggs?
A.
B.
C.
D.
mitosis
meiosis
fertilization
sexual reproduction
____ 19. Scientists have produced a genetically engineered orange tree that is resistant to disease. Which of the
following is the best example of a potential benefit to society that could result from this biotechnology?
A.
B.
C.
D.
increased cost of oranges
reduced orange crop yield
greater availability of oranges as a food source
a change in the distribution of insects that pollinate orange flowers
____ 20. Researchers in a biotechnology lab are performing a procedure. The procedure is shown in the illustration
below. They are inserting the nucleus of a cell from an adult animal into an egg cell from which the nucleus
has been removed. Applications of this procedure can impact individuals, society, and the environment.
What will develop from the structure produced in this procedure?
A. a cloned animal with the regular amount of genetic material
B. a cell that will go through meiosis but be unable to produce sperm or eggs
C. a genetically unique animal with twice the regular amount of genetic material
D. an animal that has a combination of genetic material from several different organisms
____ 21. Insulin was the first medicine produced through genetic engineering and then made available to patients. To
produce insulin, a human insulin gene is inserted into bacterial DNA. The bacteria that contain the DNA then
produce insulin. What has been a major impact of the genetic engineering of insulin?
A. Humans began to lose their ability to produce insulin.
B. Medicines became less effective because they used bacterial insulin, not human insulin.
C. More insulin, identical to the insulin produced by humans, became available for people to
use.
D. Human health was put at risk because bacteria are too small to make enough insulin to
meet medical needs.
____ 22. Near the surface of polar oceans, phytoplankton convert solar energy into chemical energy that fuels a
complex ecosystem. The food web below illustrates some relationships among organisms in the Arctic.
According to the food web, how would cod be classified?
A.
B.
C.
D.
producer
top predator
primary consumer
secondary consumer
____ 23. Energy from food moves through food webs. Which statement correctly describes this energy?
A. Food energy is energy released when food is cooked.
B. Food energy is kinetic energy that gets released when needed.
C. Food energy is chemical energy in the bonds of food molecules.
D. Food energy is the energy shared among a single species in an ecosystem.
____ 24. Energy gets transferred through the food web as plants that produce food are consumed by animals that
consume plants. The energy is further transfer through animals that consume other animals. Which statement
explains what happens to this energy when a plant dies before it is consumed?
A. The energy disappears.
B. The energy must go to new plants that grow out of dead organisms.
C. The energy can only go to an animal scavenger that eats the dead organism.
D. Decomposers that break down the dead organism take in the stored energy.
____ 25. Which of the following relationships is most like the predator-prey relationship?
A. symbiosis
B. parasitism
C. mutualism
D. commensalism
____ 26. In the four panels of drawings below, each panel shows animals living in the same area at different times.
Going from the bottom to the top panels, what behavior likely increased among the animals?
A. commensalism
B. parasitic relationships
C. mutualism between two species
D. competition for food and water
____ 27. A tapeworm attaches to the intestines of a pig. The tapeworm eats partially digested food entering the pig’s
intestine. Without enough nutrients from the food, the pig could die. In this relationship, what are the
tapeworm and the pig called?
A. The pig is the host and the tapeworm is the parasite.
B. The pig is the host and the tapeworm is the predator.
C. Both the tapeworm and the pig are called competitors.
D. The tapeworm is a predator, the pig is prey, and both are competitors.
____ 28. The illustration below shows a land ecosystem.
Which of these limiting factors can affect native populations in this ecosystem?
A. lack of water
B. lack of sunlight
C. effective drainage
D. changing conditions
____ 29. Blowing sand forms dunes along Florida’s beaches. Trees do not grow on the dunes, but small plants do. The
roots of small plants then hold the dunes in place. In what way is the sand a limiting factor on the size of
plants that can grow on the dunes?
A.
B.
C.
D.
Sand blows away before any plants can grow.
Sand cannot hold enough water for trees that grow on dunes.
Sand cannot provide enough support for plants that have large roots.
Sand does not have enough food for large plants that grow on the dunes.
____ 30. Salt marshes grow along Florida’s coast. Grasses, sedges, rushes, and other plants that need shallow water
grow in the marshes. What would most likely be a limiting factor in the growth of these salt-marsh plants?
A. rising water level
B. high levels of sunlight
C. developing the area for orange groves
D. developing the area for neighborhoods
Grade 7 Life Posttest
Answer Section
MULTIPLE CHOICE
1. ANS: C
A is incorrect because species that are alive today evolved from ancestors that were alive in the Cambrian
period.
B is incorrect because the ancestors of a species live before that species is alive.
C is correct because descendents of a species live after that species is alive.
D is incorrect because since some species in the Cambrian period shared traits with those organisms that lived
before them, they could be related.
STA: SC.7.L.15.1
2. ANS: C
A is incorrect because one field site may contain many layers of rock, each with fossils from different periods
of time.
B is incorrect because the same type of rock may form at different times in different locations.
C is correct because fossils in one layer of rock get covered by more and more layers of rock as time passes.
D is incorrect because the opposite is true: fossils that are located in deeper layers of rock are usually from
organisms that were less recently alive.
STA: SC.7.L.15.1
3. ANS: C
A is incorrect because living species of hippopotamuses had not yet evolved 45 million years ago.
B is incorrect because living species of toothed whales had not yet evolved 45 million years ago.
C is correct because at the point of the timeline corresponding to 45 million years ago, there is a branch event
suggesting that species ancestral to both hippopotamuses and toothed whales lived at that time.
D is incorrect because the species that is ancestral to both living baleen whales and living hoofed grazing
mammals existed 55 million years ago.
STA: SC.7.L.15.1
4. ANS: C
A is incorrect because the white mice and the dark mice differ only in color and presumably are equally tasty
to the hawks, but the hawks can see the white mice more easily and so eat more of them.
B is incorrect because it is not possible to make this conclusion. It is more likely that the hawks can see the
white mice more easily than the dark mice and so eat more of them.
C is correct because the white mice are more visible to the hawks, so the white mice are removed from the
population more often than the dark mice and the percentage of white mice in the population decreases.
D is incorrect because the white mice are more visible to the hawks than the dark mice are, which explains
why the percentage of white mice in the population is decreasing.
STA: SC.7.L.15.2
5. ANS: D
A is incorrect because low genetic diversity will make it harder for cheetahs to adapt to changing factors in
their environment.
B is incorrect because genetic diversity does not affect the ability to produce mutations.
C is incorrect because low genetic diversity would cause low diversity in physical traits.
D is correct because with low genetic diversity, there is a decreased chance of some individuals being highly
successful in changed conditions.
STA: SC.7.L.15.2
6. ANS: D
A is incorrect because those birds that were able to maintain nesting sites would still be able to reproduce.
B is incorrect because birds that establish nests late in the year, after other birds have already claimed nesting
sites, would not be likely to find suitable nesting sites.
C is incorrect because birds that establish nests at the time when most birds are establishing nests would face
intense competition for nesting sites.
D is correct because birds that establish nests early in the year, before other birds try to claim nesting sites,
would face less competition for nesting sites.
STA: SC.7.L.15.2
7. ANS: A
A is correct because if the rodents are able to eat plants that have also survived in the changed environment,
they will also likely be able to survive.
B is incorrect because as the climate becomes drier, the berry plant might become rare or extinct. Eating only
one type of food makes it harder for a species to withstand change.
C is incorrect because damp areas would likely become rare in a dry climate.
D is incorrect because dark coloring would not reflect heat, small ears would not be as useful as large ears in
dissipating heat, and daytime activity habits would use too much energy in a hot environment.
STA: SC.7.L.15.3
8. ANS: A
A is correct because lake trout numbers are increasing, so they could have adapted to the presence of sea
lampreys, but also it’s possible that conservation efforts helped them recover their population size.
B is incorrect because if people decided to eliminate lake trout from Lake Superior, population size would
continue declining.
C is incorrect because if either species experienced extinction, their numbers would drop to zero and would
never recover.
D is incorrect because if lake trout went extinct they would never recover, and if sea lampreys became even
deadlier then lake trout populations would continue to decline.
STA: SC.7.L.15.3
9. ANS: A
A is correct because when species go extinct, there are fewer species in the area.
B is incorrect because when species go extinct, the number of species in the area declines.
C is incorrect because when species go extinct, the number of species in the area is affected.
D is incorrect because one measure of biodiversity is the number of species present in an area.
STA: SC.7.L.15.3
10. ANS: A
• A is correct because DNA contains the set of instructions that determines traits, such as eye color and hair
color.
• B is incorrect because glucose is a sugar molecule.
• C is incorrect because cellulose is a starch molecule.
• D is incorrect because cholesterol is a lipid molecule.
STA: SC.7.L.16.1
11. ANS: B
A is incorrect because the illustration shows a DNA molecule, not a carbohydrate.
B is correct because the illustration shows a DNA molecule.
C is incorrect because the illustration shows a DNA molecule, not a lipid.
D is incorrect because the illustration shows a DNA molecule, not a protein.
STA: SC.7.L.16.1
12. ANS: A
A is correct because meiosis forms sperm and egg cells, which combine hereditary information in a new
generation upon fertilization.
B is incorrect because mitosis is not involved in the transfer of hereditary information between generations,
and chromosomes are not considered to be a process.
C is incorrect because neither of these processes is directly involved in the transfer of hereditary informtion
between generations.
D is incorrect because, with a very few exceptions, animals do not reproduce asexually, and DNA replication
is not directly involved in the transfer of hereditary information.
STA: SC.7.L.16.1
13. ANS: A
• A is correct because there is a 1 in 4 chance that an offspring will inherit the alleles PP.
• B is incorrect because there is a 2 in 4, or 50% chance that an offspring will inherit the alleles Pp.
• C is incorrect because each offspring is twice as likely to inherit Pp as it is to inherit PP.
• D is incorrect because each offspring is more likely to inherit Pp than it is to inherit pp.
STA: SC.7.L.16.2
14. ANS: D
A is incorrect because a cross of Rr with Rr would yield 25% of offspring with the genotype rr and, therefore,
wrinkled seeds.
B is incorrect because a cross of Rr with Rr would yield 25% of offspring with the genotype rr and, therefore,
wrinkled seeds.
C is incorrect because a cross of Rr with Rr would yield 25% of offspring with the genotype rr and, therefore,
wrinkled seeds.
D is correct because a cross of Rr with Rr would yield 25% of offspring with the genotype rr and, therefore,
wrinkled seeds.
STA: SC.7.L.16.2 | SC.7.N.1.1
15. ANS: D
A is incorrect because the genotype in that position is AA not aa.
B is incorrect because the genotype in that position is AA not aA. Note that aA is not standard annotation, but
is the same genotype as Aa.
C is incorrect because the genotype in that position is AA not Aa.
D is correct because the genotype in that position is AA.
STA: SC.7.L.16.2 | SC.7.N.1.1
16. ANS: B
A is incorrect because sexual reproduction increases genetic diversity, but asexual reproduction does not.
B is correct because asexual reproduction requires only one parent, and sexual reproduction requires two
parents.
C is incorrect because sexual reproduction increases a species’ chances of surviving unfavorable conditions,
but asexual reproduction does not.
D is incorrect because the offspring produced by sexual reproduction are not identical to each other, but those
of asexual reproduction are identical to each other.
STA: SC.7.L.16.3
17. ANS: A
A is correct because the new plant grew by asexual reproduction, involving only mitosis.
B is incorrect because this is asexual reproduction and does not involve meiosis.
C is incorrect because this is asexual reproduction and does not involve meiosis.
D is incorrect because this is asexual reproduction and does not involve meiosis.
STA: SC.7.L.16.3
18. ANS: B
A is incorrect because mitosis produces cells identical to the parent cell, not sperm and eggs.
B is correct because meiosis is the process that produces sperm and eggs, or gametes.
C is incorrect because fertilization is the process that joins sperm and egg, not the process that produces sperm
and eggs.
D is incorrect because sexual reproduction is a process that requires sperm and eggs, not the process that
produces sperm and eggs.
STA: SC.7.L.16.3
19. ANS: C
• A is incorrect because an increased cost of oranges would not be a benefit to society.
• B is incorrect because reduced orange crop yield would not be a benefit to society.
• C is correct because greater availability of oranges as a food source would benefit society.
• D is incorrect because it is not clear whether a change in the distribution of insects that pollinate orange
flowers would have a positive, neutral, or negative effect on society.
STA: SC.7.L.16.4
20. ANS: A
A is correct because the illustration shows the cloning of an animal: a nucleus is being inserted into an egg
from which the nucleus has been removed.
B is incorrect because the cell shown is an egg with a complete set of DNA that will go through mitosis as it
develops, not a sex cell that will go through meiosis.
C is incorrect because the cell shown is a cloned cell that has the regular amount of genetic material.
D is incorrect because there is only genetic information from one organism shown in the image—the nucleus
being inserted into the egg.
STA: SC.7.L.16.4
21. ANS: C
A is incorrect because the production of insulin by bacteria is unrelated to a person’s ability to produce
insulin.
B is incorrect because the gene used to produce insulin is a human gene, not a bacterial gene.
C is correct because the insertion of a human insulin gene into bacterial DNA results in the bacteria producing
human insulin, the protein for which the gene codes.
D is incorrect because the small size of bacteria allows for efficient production of large quantities of insulin; it
does not restrict the amount that can be produced.
STA: SC.7.L.16.4
22. ANS: D
A is incorrect because a producer uses the energy from sunlight.
B is incorrect because top predators are generally tertiary consumers that are not eaten by other organisms,
such as the polar bear.
C is incorrect because primary consumers feed on producers.
D is correct because secondary consumers are organisms that feed on primary consumers.
STA: SC.7.L.17.1
23. ANS: C
A is incorrect because food energy is a specific type of energy.
B is incorrect because food energy is not the energy of motion.
C is correct because food energy is chemical energy that is released as its bonds are broken.
D is incorrect because food energy is transferred to different species throughout a food web.
STA: SC.7.L.17.1
24. ANS: D
A is incorrect because the stored energy cannot disappear, it must take a new form.
B is incorrect because decomposers break down dead organisms.
C is incorrect because scavengers do not eat all the organisms that die.
D is correct because in breaking down dead and decaying organisms, decomposers take in the energy stored
in the organism.
STA: SC.7.L.17.1
25. ANS: B
A is incorrect because although the organisms involved in a predator-prey relationship have some dependency
on each other, symbiosis is not specific enough to refer to this kind of relationship.
B is correct because in parasitism, and in a predator-prey relationship, one of the organisms benefits at the
other’s expense.
C is incorrect because in mutualism, both of the organisms benefit, but in predator-prey relationships, prey
often does not benefit from the predator.
D is incorrect because in commensalism, one of the organisms is unaffected, but in the predator-prey
relationship, both of the organisms are affected.
STA: SC.7.L.17.2
26. ANS: D
A is incorrect because increased numbers of organisms would not lead to commensalism.
B is incorrect because parasitic relationships would not likely result frorm increased numbers of animals.
C is incorrect because mutualism, in which two or more animals benefit from a relationship, would not be an
outcome of increase numbers of animals.
D is correct because more animals crowded into the same area leads to increased competition for resources,
such as food and water.
STA: SC.7.L.17.2
27. ANS: A
A is correct because the tapeworm is a parasite living off of the pig, the host.
B is incorrect because the tapeworm does not capture and eat the pig.
C is incorrect because the tapeworm and the pig are not directly competing for resources.
D is incorrect because the tapeworm does not eat the pig and they do not directly compete for resources.
STA: SC.7.L.17.2
28. ANS: D
• A is incorrect because dunes are located near the ocean, which is a source of water and can contribute to a
wet climate.
• B is incorrect because the lack of tall shade trees and land features on the dunes means that there is plenty of
sunlight.
• C is incorrect because the sandy soil of the dunes drains effectively, so this is not a limiting factor for this
ecosystem.
• D is correct because climate conditions and ocean waves affect the steep, shifting soil of dunes. This soil can
cover plants and shelters over time.
STA: SC.7.L.17.3
29. ANS: C
A is incorrect because small plants grow on dunes and hold the sand in place.
B is incorrect because trees do not grow on dunes.
C is correct because sand is too loose to support large roots.
D is incorrect because large plants do not grow on dunes.
STA: SC.7.L.17.3
30. ANS: A
A is correct because rising tides could bring in too much water for salt marsh plants to grow close to the
ocean.
B is incorrect because the light-level requirements of the salt-marsh plants was not discussed.
C is incorrect because orange trees, like other trees, cannot grow in a salt marsh.
D is incorrect because the ground under salt marshes is too wet and unstable to build on.
STA: SC.7.L.17.3