Vervet monkeys use different alarm calls to warn each other of nearby

OFFICIAL EXPLANATION

The situation in the stimulus is that vervet monkeys use different calls depending on where predators come from. The correct answer must explain why the calls are different (again, difference versus similarity is an issue). Note that the stimulus does not contain a true paradox, just an odd situation that is presented without explanation.

Answer choice (A): This answer states that vervet monkeys vary the calls in order to indicate the number of predators, but the answer does not explain why different calls are used for land versus air predators. This answer is attractive because it shows that different calls can be used to indicate different things, but it is wrong because it does not explain the behavior of the monkeys as described in the stimulus.

Answer choice (B): This answer addresses only land-based predators and does not explain the difference described in the stimulus.

Answer choice (C): This answer states that the predators using land attacks are different from the predators using air attacks, but this information does not explain why vervet monkeys use different calls to indicate that fact.

Answer choice (D): This is the correct answer. Because vervet monkeys react to predators in different ways, they would need to know if the predator was coming by land or air. Hence, the different calls are used to tell the monkeys whether they should climb trees or dive into the foliage. Since this answer explains the behavior of vervet monkeys, this answer is correct.

Answer choice (E): The diet of selected predators of vervet monkeys is irrelevant and does not help explain why vervet monkeys use different calls depending on the direction of the attack.