单项选择题

案例分析题

Bears vary as much in character and habits as they【C1】______in size.Although a few kinds，such as grizzlies and polar bears，are fierce，most are【C2】______and only become violent when their food supplies or young are【C3】______.【C4】______to common belief，they will not hug victims to death.They are usually quiet【C5】______when feeding or when challenged by other bears.
Except during the mating season，bears live【C6】______lives.They prefer to roam in areas【C7】______by humans.Most tend to stay within certain【C8】______Black bears，【C9】______，usually stay within an area of about 14square miles （36square kilometers）.Although they remain【C10】______a particular range，most bears do not have a【C11】______resting place，preferring【C12】______to wander.
Despite the fact that bears in the wild are used to【C13】______，most of them can【C14】______easily to life in captivity.Zookeepers agree that bears are【C15】______the shrewdest and most【C16】______of animals kept in zoos.Performing bears have been popular features in【C17】______since the Middle Ages.They can be taught such tricks【C18】______wrestling and boxing，dancing，blowing a bom，riding a bicycle，and sliding on a toboggan.
Survival in the wild can be【C19】______for bear cubs.They begin life as hairless，extremely small，and helpless creatures【C20】______to open their eyes for about a week.A 200-pound （90-kilogram）black bear may have cubs weighing only 8ounces （230grams ）each.Even a newborn grizzly weighs only about 1pound （0.5kilogram）and measures only 9inches （23centimeters）from the tip of the nose to the tip of the tail.There are from one to four，but usually two，cubs to a litter born anytime between November and March.

【C1】（）

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