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下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。
How Animals Keep Warm
Man has invented ways to keep warm, but how do animals defend themselves? They can not reason in the sense that man can, but nature has taken care of the animal kingdom by providing animals with special instincts. One of these instincts is known as hibernation.
"Sleeping like a dormouse " is not only a common saying but is a reality. When winter comes, the dormouse and other hibernating animals have reached a well-nourished state. They eat very well in warmer days laying down fat in the tissues of their bodies and during hibernation this keeps them alive. Safe in their nests, or burrows, they sleep soundly until the warmth of spring arrives.
Bats, tortoises, snakes, even insects like butterflies, hibernate more or less completely. Some, like the squirrels, sleep during coldest weather but are roused by a warm spell. During hibernation, the temperature of an animal's body drops drastically. Breathing and heartbeats almost cease.
Another instinctive method of avoiding intense cold is to escape by means of migration. Wild swans, seagulls, swallows and cuckoos are a few of the very many kinds of birds which fly thousands of miles, twice a year, to avoid cold. Many animals. Especially those of the Arctic regions, have summer and winter quarters. The Arctic deer of North America, as well as the reindeer of Europe, move southward towards the forests when winter approaches. They return to the northern area when the warmth of spring begins to be sensed.
There are animals which do not attempt to leave at the first sign of winter cold. Their instinctive means of defense is to dig out a deep burrow, made soft and warm by padding out with straw, leaves, moss and further. In it they have a " secret place " containing food which they hope will last the winter through! Animals which fall into this class include the Arctic fox, the rabbit and the ermine, and the little field-mice.
1. How does the dormouse defend itself against cold in winter?
A) It moves about to keep warm.
B) It grows thicker fur.
C) It sleeps continuously.
D) It goes to warmer areas.
2. What keeps animals alive during hibernation?
A) The fat stored in their bodies.
B) Their thick fur.
C) Their warm burrows.
D) Their deep sleep.
3. During hibernation, animals breathe
A) normally.
B) at a slower rate.
C) at a faster rate.
D) irregularly.
4. According to the passage, what is " migration"?
A) Moving from one place to another with the season.
B) Living in burrows in winter.
C) Travelling in the winter months.
D) Leaving one's own country for another.
5. How does ermines survive in winter?
A) They leave their cosy burrows and migrate to warmer lands.
B) They sleep soundly inside their burrows in winter.
C) They dig out burrows and store them with enough food.
D) They stay in their burrows and live on the food stored there.
