What's this? Please answer with an explanation

A. Resource availability sets the limit.

Explanation:

The availability of resources actually affects the carrying capacity by setting a limit to it.   The carrying capacity of an environment is known to be the maximum population size which can be sustained in that environment by the given resources like food, water, habitat, and others. Such availability of resources will determine the limit of the population in that environment. This then means that if the carrying capacity exceeds the available resources it will result to an adverse effect on the environment.

answer; polycythemia is the correct answer;