Premise: 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.

Explanation: Using of different alarms by vervet monkeys to alert one another of nearby predators and where the danger is coming from; whether land or air, is to help prepare them to protect themselves. As such, the vervet monkeys can result in a solution to help themselves prevent an attack from predators. If the danger is coming from land, then the best preventive approach for the vervet monkeys is to climb the trees, however, if the danger comes from the air, the vervet monkeys can dive into foliage.

Let's observe each option and see which option fits into the explanation above as regards the behavior of vervet monkey.

Option A - Incorrect:
The varying alarm calls are to alert vervet monkeys of where the danger is coming from whether land or air and not to indicate the number of predators approaching.

Option B - Incorrect:
This claim is wrong because the passage didn't provide statistics on the numbers of vervet monkey death caused by different land-based predators.

Option C - Incorrect:
No, this is not true. The importance of the varying alarm calls by the vervet monkeys is to alert them of the possible danger approaching them. It doesn't mean that they cannot be attacked by predators.

Option D - Correct:
This claim describes the behavior of vervet monkey as expressed in the explanation provided to this solution. The varying alarm calls help the vervet monkeys to result in a solution to help themselves prevent an attack from predators. So, if the danger is coming from land, then the best preventive approach for the vervet monkeys is to climb the trees, and if the danger comes from the air, the vervet monkeys can dive into the foliage.

Option E - Incorrect:
This is not true as we cannot validate this claim from the passage.