The correct answer is C. the wolves increased the population by eating beaver's predators.
When wolves were reintroduced to Yellowstone National Park in the mid-1990s, they helped control the population of elk, which had previously overgrazed the landscape. This overgrazing had negative effects on the habitat for beavers, as willows and other vegetation were depleted. By reducing the elk population, wolves allowed these plants to regenerate. As a result, beavers were able to thrive once again, leading to an increase in their population.