What is a distinctive feature of the pronghorn's appearance?

The distinctive feature of the pronghorn's appearance that stands out is the large black markings on the face. These markings are a notable characteristic and contribute to the pronghorn's unique look among North American mammals. The black facial markings help in camouflage and may also play a role in social interactions within their species.

In contrast to the correct choice, pronghorns have relatively large ears, which are not small; their tails are not particularly long as compared to other similar animals; and while they do have a fur coat, it isn't specifically categorized as shaggy in the way other animals might be. Thus, the most recognizable feature that sets pronghorns apart is indeed the striking black facial markings.