填空题

American black bears (11) in a variety of colors despite their name. In the eastern part of their range, most of these brown, red, or even yellow coats. To the north, the black bear is actually gray or white (12) . Even in the same litter, both brown and black furred bears may be born.
Black bears are the smallest of all American beam, ranging in length from five to six feet, weighing from three hundred to (13) pounds. Their (14) are small and their eyesight and hearing are not as good as their sense of smell. (15) all bears, the black bear is timid, clumsy, and rarely dangerous. But if attacked, most can climb trees and cover ground at great speeds. When angry or frightened, it is a formidable enemy.