For a character trait to evolve in a population, it must:
a. be heritable, mutate, and affect reproductive success
b. be hidden, vary in the population, and affect reproductive success.
c. mutate, affect reproductive success, and cause disequilibrium
d. vary in the population, affect reproductive success, and be heritable.

The correct answer will be option A.

Explanation:

The evolution of an organism depends on the degree of adaptation in any particular niche that is the success of a trait is selected by nature.

An individual acquires a useful trait in a population due to the change at the genetic level in the genes or mutation in the sequence of DNA. The trait to become permanent in the population has to be passed on to the generations that are the trait should be inherited. If a trait is useful must increase the reproductive rate of species that is would increase the rate of survival.

Thus, option A is the correct answer.