The fertility rate at which a population will remain constant is referred to as

The fertility rate at which a population will remain constant is called ZERO POPULATION GROWTH. At the point of zero population growth, there is demographic balance and the number of people in the specified population is not growing neither are they declining.

B. Selective breeding and genetic engineering.

Explanation:

The goal of selective breeding is to produce organisms that have a disered trait through only breeding said specis with that traits. (for example, farming breeds animals that are better for food.)

The goal of genetic engineering is to take a trait from one organism and apply it to another. (For example, putting artic fish gentics into a tommat so that it won't freeze.)  

In conclusion, both of these processes serve the common goal of creating more disered organisms artifically.