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  3. Hibernation Hibernation is one of the main adaptations that allow certain northern animals to survive 【1】, cold winters. Hib

Hibernation Hibernation is one of the main adaptations that allow certain northern animals to survive 【1】, cold winters. Hib

admin2012-05-23  69
问题     Hibernation
    Hibernation is one of the main adaptations that allow certain northern animals to survive 【1】, cold winters. Hibernation is like a very deep sleep that allows animals to save their energy when there is little or【2】food available. The body functions of "true hibernators" go through several changes【3】they are hibernating. Body temperature drops, and the heart rate 4 . For example, a hibernating woodchuck’s body temperature drops by more than 30 degrees Celsius, and its heart rate is down from 80 to【4】beats per minute! Other true hibernators include the jumping mouse, little brown bat, eastern chipmunk, and several ground squirrels. Other animals, such as the skunk and raccoon, are not considered true hibernators,【5】they wake up in the winter to feed, and their body【6】do not change as much. Since they only sleep for a little bit at a time, the term dormancy or "light sleeping" is used to describe their behavior.
    The largest animals to hibernate are bears. Their heart rate may slow down from a usual 40 -50 beats per minute to 8-12 beats per minute,【7】their body temperature changes very little, so they are able to wake up quickly.
    Hibernating animals have a special substance in the blood called hibernation inducement trigger, or HIT. This substance becomes active in the fall, when the days become cooler and shorter. When HIT becomes active, the animals start【8】for winter. Some animals store food so that they can eat when they wake up, and some animals eat a lot in late summer and fall to add excess fat to their bodies. This fat keeps them warmer and acts【9】a source of energy while they are sleeping. Some animals also make changes to the places【10】they will sleep. They add leaves and grasses to keep them warm.
选项 A、for
B、but
C、as
D、since
答案B
解析
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