A population of animals feeds entirely on plants. Some of these animals are good at digesting Plant A, while others are good at digesting Plant B, and others are good at digesting Plant C. What might be an advantage of a single population of animals having a large amount of variability surrounding certain traits?

It increases the chance that some members of the population will survive under changing environmental conditions.

Explanation:

Variation of traits between organisms within and among species increases the chance that some members of the population will survive under changing environmental conditions.

If, for example, a disease reduces the amount of Plant A and Plant B in the environment, some members of the animal population will still survive. Since the population can survive on a variety of plants, those that can eat Plant C will be less affected by the disease and will still be successful.

There's less scarcity of food for the population is an advantage of a single population of animals having a large amount of variability surrounding certain traits

Explanation:

The population of animal is eating three different types of plants. One of them is good in digesting plant A, one of them is good in digesting plant B and other group is good in digesting plant C.

Thus, the population although has a huge number, but each of the individual is divided into one of the 3 groups which is different in feeding habits. Thus there's no scarcity of food in the population. Thus the population can live well and reproduce without any nutritional strain.