阅读理解：阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项．

　　Imagine you are a left-hander, Suddenly everything in the world is changed. The dour locks are on the wrong side and turn the wrong way.

　　Twenty-five million Americans wake up every day in just such a sorry situation. There are one in ten of us who are left-handed and must face the world designed for the right-handed majority.

　　Why we are left-or right-handed remains a secret. We know that nearly two out of three lefties are men and that left-handedness runs in families. According to one study almost half of the children of two left-handed parents will be left-handed. The Scots-Irish family Kerr produced so many left handers that in 1470 the family built its house stairway with a reverse twist (盘旋).

　　On the other hand, heredity (遗传) alone cannot explain lefties. At least 84 percent of them are born of two right-handed parents. And in 12 percent of twins, one will be right-handed, the other left.

　　Perhaps the greatest puzzle of all is not why some people are left-handed, but rather why so few are. In fact, almost equal numbers of individuals (个人) will favor either the right or the left. However, scientists are trying to set things right and they are beginning to study the many ways left-handers differ from right-handers by considering how their brains work.

1．How many of the Americans are left-handers?

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2．Which of the following is NOT true?

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A．A left handed man may have a right-handed twin brother.

B．The greater part of left-handers have right-handed parents.

C．One in ten of Americans are left-handed.

D．Most people will prefer the right to the left.

3．From the passage, we can see that________.

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A．there is at least a left-hander in every American family

B．left-handers are generally cleverer than right-handers

C．most people all over the world are right-handers

D．left-handers lead an uncomfortable life

4．In Paragraph 3, the underlined word “runs” means ________.

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5．Why so few people are left-handed________.

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A．has nothing to do with heredity

B．is not known to scientists

C．has little to do with the working of their brains

D．is that left-handers are mainly twins