When geographers study an environment's capacity, they study the population that can be sustained by the environment's resources.
a. governmental
b. carrying
c. urban
d. natural

The answer is: b. carrying.

An environment's carrying capacity of a species in an environment is the maximum population size of the species that the environment can sustain.

Geographers use carrying capacity to describe the number of living organisms that could feed on some segment of land without destroying it.

The carrying capacity could support a positive natural increase or could require a negative natural increase (difference between the birth rate and the death rate).