题目列表(包括答案和解析)
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When did you last see a polar bear(北极熊）?On a trip to a zoo,perhaps?If you had attended a winter activity in New York a few years ago,you would have seen a whole polar bear club.These "Polar Bears" are people who meet frequently in the winter to swim in freezing cold water.That day,the air temperature was 3℃,and the water temperature was a little higher.The members of the Polar Bear Club at Coney Island,New York are usually about the age of 60.Members must satisfy two requirements.First,they must get along well with everyone else in the group;this is very important because there are so many different kinds of people in the club.Polar Bears must also agree to swim outdoors at least twice a month from November to February.
Dcotors don't agree about the medical effects of cold-winter swimming.Some are worried about the dangers of a condition in which the body's temperature drops so low that finally the heart stops.Other doctors,however,point out that there is more danger of a heart attack during summer swimming because the difference between the air temperature and water temperature is much greater in summer than in winter.
The Polar Bears themselves are satisfied with the benefits of cold-water swimming.They say that their favorite form of exercise is very good for the circulatory system(循环系统）because it forces the blood to move fast to keep the body warm.Cold-water swimmers usually turn bright red after a few minutes in the water.A person who turns blue probably has a very poor circulatory system and should not try cold-water swimming.
The main benefits of cold-water swimming are probably mental.The Polar Bears love to swim all year round;they find it fun and relaxing.As one 70-year-old woman says,"When I go into water,I pour my troubles into the ocean and let them float away."
72.The members of the Polar Bear Club must meet the following requirements except that_____.[来源:学+科+网]
A.they must swim outdoors at least 8 times in the four cold months
B.they must reach the age of 60
C.they should be easy to make friends with
D.they must agree to swim outdoors from November to February
73.According to the passage,some doctors believe it is true that_____.
A.Polar Bears are bears swimming in freezing water
B.cold-water swimming can make the body temperature dangerously high
C.you are healthy if cold-water swimming turns your skin color blue
D.cold-water swimming causes more heart attacks in summer than in winter
74.The Polar Bears like to swim year-round,for_____.
A.it is an easy way ot keep the body warm in winter
B.they can remain young
C.they find it enjoyable and interesting
D.they might meet fewer troubles in life
75.The passage is mainly about_____.[来源:]
A.the requirements of the Polar Bear Club
B.a group of cold-water-swimming livers
C.the Polar Bears' life in New York
D.doctors' ideas about cold-water swimming
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请认真阅读下列短文，并根据所读内容在文章后表格中的空格里填入一个最恰当的单词。
For more than twenty years scientists have been seeking to understand the mystery of the‘‘sixth sense"of direction．By trying out ideas and solving problems one by one, they are now getting closer to one answer．
One funny idea is that animals might have a built-in compass(指南针)．
Our earth itself is a big magnet(磁体)．So a little magnetic needle that swings freely lines itself with the big earth magnet to point north and south．When people discovered that idea about athousand years ago and invented the compass, it allowed sailors to navigate(航海)on oceanvoyages, even under cloudy skies．
Actuallly the idea of the living compass came just from observing animals in nature．
Many birds migrate twice a year between their summer homes and winter homes．Some of them fly for thousands of kilometers and mostly at night．Experiments have shown that some birds can recognize star patterns．But they can keep on course even under cloudy skies．How can they do that?
A common bird that does not migrate but is great at finding its way home is the homing pigeon．Not all pigeons can find their way home．Those that can are very good at it, and they have been widely studied．
One interesting experiment was to attach little magnets to the birds' heads to block their magnetic sense－just as a loud radio can keep you from hearing a call to dinner．On sunny days, that did not fool the pigeons．Evidently they can use the sun to tell which way they are going．But on cloudy days, the pigeons with magnets could not find their way．It was as if the magnets had blocked their magnetic sense．
Similar experiments with the same kind of results were done with honeybees．These insects also seem to have a special sense ot direction．
In spite of the experiments, the idea of an animal compass seemed pretty extraordinary．How would an animal get the magnetic stuff for a compass．
An answer came from an unexpected source．A scientist was studying bacteria that live in the mud of ponds and marshes．He found accidentally little rod-like bacteria that all swam together in one direction－north．
Further study showed that each little bacterium had a chain of dense particles inside, which proved magnetic．The bacteria had made themselves into little magnets that could line up with the earth's magnet．
The big news was that a living thing, even a simple bacterium, can make magnetite．That led to a search to see whether animals might have it．．By using a special instrument called magnetometer, scientists were able to find magnetite in bees and birds, and even in fish．In each animal, except for the bee．the magnetic stuff was always in or closer to the brain．
Thus．the idea of a built－in animal compass began to seem reasonable．
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