The correct answer is option B, that is, increased availability of food.
The carrying capacity of a biological species in surrounding refers to the majority of the size of the population of the species, which the environment can maintain indeterminately, given the habitat, food, water, and other essential necessities in the environment.
In terms of population biology, carrying capacity is illustrated as the maximum load that can be handled by the environment. Thus, in the given case, the carrying capacity of the prairie dogs in an area gets increased with the increase in the availability of food.