When we are talking of advantages in the competition for resources, there are several factors that we must take into account. In the case of a mountain lion as it said is an apex predator, however, is not a specialist predator as is the case of cheetahs, this means that it can feed of several different prays, therefore the conditions that will confere it advantage it will depend on the pray, and the season. Taking this into account we can proceed to analyze the provided characteristics.
A spotted coat can provide better camouflage, although as it is a template forest their habitat it hasn't the same advantage that it would have on the steppe or tropical forests. In the case of short fur, is more related to thermoregulation functions, and as it is a cold environment it wouldn't confer an advantage. Long legs can provide an advantage in running, nonetheless, template forests, are mountainous paths so major velocity is not necessarily better. Abundant whiskers are involved insensitivity, they would permit a better perception of the surroundings, including small movements of the prey, as well a more stealth movement. considering all these abundant whiskers (option D) would provide an advantage.