The correct answer is D. limiting resources.
The carrying capacity of a population is the maximum number of individuals that a particular environment can support indefinitely. It is determined by the availability of limiting resources, such as food, water, and shelter. When a population exceeds its carrying capacity, the resources available to each individual decrease, and the population begins to decline.
A. Population growth rate is the rate at which a population increases in size. It is determined by the birth rate and the death rate.
B. Natality is the birth rate of a population. It is the number of births per unit time per capita.
C. Mortality is the death rate of a population. It is the number of deaths per unit time per capita.
All of these factors can affect the carrying capacity of a population, but the most important factor is the availability of limiting resources.