Which of the following is a living factor in an ecosystem that could limit the size of a raccoon population?
a. a forest fire
b. a very cold winter
c. the availability of water
d. competition from other animals

The correct answer is D. competition from other animals.

In any ecosystem, living organisms grow in a geometric progression and resources are grown in an arithmetic progression. Hence, resources such as food and space become limited. Short supply of resource cause competition for food, space among organisms. Competition may be interspecific or intraspecific. In interspecific competition for food and space among the individuals of different species. in intraspecific, competition among the individuals of same species. Therefore, to limit the size of a raccoon population, the living factor is the competition. Forest fire , a very cold winter  and the availability of water are non-living or abiotic factors.