A
It states the conclusion.
B
It is offered as support for the conclusion.
C
It attempts to spell out the practical implications of the critic’s conclusion.
D
It attempts to explain the nature of the distinction that the critic considers.
E
It attempts to anticipate an objection to the critic’s conclusion.
A recent study examined the daytime and nighttime activity patterns of two populations of tree-dwelling lemurs—the first living in a rain forest, where tree canopy cover is consistent year-round, and the second living in a deciduous forest, where many trees lose their leaves during the winter months. Both groups of lemurs were found to be more nocturnal during winter months than they were the rest of the year. However, the winter increase in nocturnal activity was significantly more pronounced for the population living in the deciduous forest than it was for the population living in the rain forest.
"Surprising" Phenomenon
Why does winter nocturnal activity increase much more for tree-dwelling lemurs in a deciduous forest, where trees lose leaves in winter, compared to those in a rainforest, where tree canopy cover stays the same all year?
Objective
The correct answer will propose a hypothesis explaining a key factor that causes lemurs in a deciduous forest to have more winter nocturnal activity than those in a rainforest. This factor must depend in some way on the tree canopy cover in the forest and will thus affect the lemurs’ behavior differently depending on their environment.
A
For both lemur populations, the primary competitors for food resources are species active during daylight.
The fact that both lemur populations’ competitors are active during daylight has nothing to do with tree canopy cover and does not explain why lemurs in the deciduous forest had much more nocturnal activity than those in the rainforest.
B
The primary predators for both lemur populations are high-flying birds that rely on their eyesight to hunt prey during daylight.
Lemurs in deciduous forests face greater predation risk in winter because the birds can see clearly without leaves. In rainforests, year-round leaves block these predators' view. Thus, to avoid predators, lemurs in deciduous forests are more active at night during the winter.
C
In both habitats, species of predatory snakes active during daylight are most active during winter months.
This might explain why both populations are more nocturnal during the winter. However, because the snakes’ hunting isn’t affected by tree canopy cover, it doesn’t explain why lemurs in deciduous forests have more nocturnal activity than those in rainforests during the winter.
D
The lemur population in the rain forest is twice the size of the population in the deciduous forest.
Population size doesn’t explain why the lemur population in the deciduous forest has more nocturnal activity in the winter than the lemur population in the rainforest. We need a factor that affects the lemurs differently based on the tree canopy cover of their environments.
E
The lemur population in the rain forest eats both plants and insects whereas the population in the deciduous forest eats only plants.
Why would eating only plants cause the lemurs in the deciduous forest to have more nocturnal activity in the winter? We still need a factor that affects the lemurs’ winter behavior differently based on the tree canopy cover of their environments.
A
presumes, without providing justification, that a claim cannot be true if those who advance it are motivated by snobbery
B
takes for granted that anyone who is motivated purely by snobbery cannot also be motivated by legitimate historical evidence
C
fails to consider adequately the possible motives of those who claim that Shakespeare did write the plays commonly attributed to him
D
fails to exclude the possibility that there might be legitimate evidence motivating those who reject Shakespeare’s authorship
E
makes use of an assumption that one would accept only if one has already accepted the truth of the conclusion