GMAT Critical Reasoning (CR) | Re: Vervet monkeys use different alarm calls to warn

Vervet monkeys use different alarm calls to warn each other of nearby predators, depending on whether the danger comes from land or from the air.
Which one of the following, if true, contributes most to an explanation of the behavior of vervet monkeys described above?
A. By varying the pitch of its alarm call, a vervet monkey can indicate the number of predators approaching.
B. Different land-based predators are responsible for different numbers of vervet monkey deaths.
C. No predators that pose