PrepTest 122, Section 1, Question 8

What we’re looking for

Working the answers

• A

  This explains how a call could communicate the number of predators. Our question concerns their location: danger from the ground versus danger from the air. Knowing whether there are one or five predators is different information, so A leaves the reason for this particular distinction unexplained.

• B

  This compares different predators within the land-based group. Maybe one land predator kills more monkeys than another, but that doesn't explain a different call for land predators as a group versus predators in the air. We need an explanation of the distinction the passage actually gives us.

• C

  This separates land predators from air predators, so it initially looks relevant. But why would monkeys need different calls for the two groups? If the same escape response worked for every predator, a single warning could still be useful. Knowing that no predator attacks from both places doesn't establish a reason the monkeys benefit from specifying which place the danger comes from.

• D
  Correct

  The appropriate escape response changes with the direction of the threat. For a land predator, the monkeys climb trees. For an aerial predator, they dive into foliage. A distinct alarm tells the other monkeys which response to use. That connects the information in the call to something useful the monkeys can do with it, exactly what our prediction sought.

• E

  I don't need to know what else a predator eats. A bird that also eats other animals can still threaten a vervet monkey. A land predator that eats only vervet monkeys can threaten one too. The difference in their diets doesn't explain why monkeys should signal the source of the danger differently.