单选题 Learning disabilities are very common. They affect perhaps 10 percent of all children. Four times as many boys as girls have learning disabilities.
Since about 1970, new research has helped brain scientists understand these problems better. Scientists now know there are many different kinds of learning disabilities and that they are caused by many different things. There is no longer any question that all learning disabilities result from differences in the way the brain is organized.
You cannot look at a child and tell if he or she has a learning disability. There is no outward sign of the disorder. So some researchers began looking at the brain itself to learn what might be wrong.
In one study, researchers examined the brain of a learning-disabled person, who had died in an accident. They found two unusual things. One involved cells in the left side of the brain, which control language. These cells normally are white. In the learning-disabled person, however, these cells were gray. The researchers also found that many of the nerve cells were not in a line the way they should have been. The nerve cells were mixed together.
The study was carried out under the guidance of Norman Geschwind, an early expert on learning disabilities. Doctor Geschwind proposed that learning disabilities resulted mainly from problems in the left side of the brain. He believed this side of the brain failed to develop normally. Probably, he said, nerve cells there did not connect as they should. So the brain was like an electrical device in which the wires were crossed.
Other researchers did not examine brain tissue. Instead, they measured the brain"s electrical activity and made a map of the electrical signals.
Frank Duffy experimented with this technique at Children"s Hospital Medical Center in Boston. Doctor Duffy found large differences in the brain activity of normal children and those with reading problems. The differences appeared throughout the brain. Doctor Duffy said his research is evidence that reading disabilities involve damage to a wide area of the brain, not just the left side.

单选题 Scientists found that the brain cells of a learning-disabled person differ from those of a normal person in ______.

【正确答案】 D

【答案解析】[解析] 该题的答案见第四段，科学家发现正常情况下为白色的这些细胞，在学习低能症患者大脑中却变为灰色(In the learning-disabled person, however, these cells were gray)，同时他们还发现many of the nerve cells were not in a line the way they should have been. The nerve cells were mixed together.(这些神经细胞有许多没有按它们应有的方式排列，而是混合在一起。)故D为正确选项。

单选题 Which of the following is NOT mentioned in the passage?

单选题 All of the following statements are true EXCEPT that ______.

【正确答案】 C

【答案解析】[解析] 此题为正误识别题。根据全文内容，可发现只有选项C与第一段：Learning disabilities are very common. They affect perhaps 10 percent of all children. Four times as many boys as girls have learning disabilities.(学习能力低下是一种常见现象，所有儿童中受到影响的大概有10%。男童中学习能力低下的人数是女童的4倍。)的内容不符。文中为影响全部儿童的10%，而不是全部人口的10%，故选项C正确。

单选题 Doctor Duffy believed that ______.

【正确答案】 B

【答案解析】[解析] 此题的答案见最后一段的末尾：Doctor Duffy found large differences in the brain activity of normal children and those with reading problems. The differences appeared throughout the brain. Doctor Duffy said his research is evidence that reading disabilities involve damage to a wide area of the brain, not just the left side.可见选项B为正确答案。

单选题 According to the passage we can conclude that further researches should be made ______.

【正确答案】 A

【答案解析】[解析] 该题为判断题，其答案见对整个短文的综合理解。纵观全文，所讨论的主要问题为有学习障碍的人的大脑发育及其组织结构，而根据两位医生的发现，可以推断：他们下一步的工作应该是找出产生这一差别的原因，为儿童的正常发育提供正常的条件，故选项A符合本题的意思，为正确答案。短文没有涉及选项B(研究儿童如何读写和使用数字)、C(帮助学习上弱智的儿童去提高智力)和D(探索语言学习中大脑左侧的功用)。