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 the 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______.
单选题
Which of the following is NOT mentioned in the passage?
【正确答案】
A
【答案解析】解析：文章最后一段提到“Doctor Duffy said his research is evidence that reading disabilities involve damage to a wide area of the brain，not just the left side．”可见文中提到了B项，无学习能力可能是由脑部许多部位的损伤导致的。第二段“There is no longer any question that all learning disabilities result from differences in the way the brain is organized．”所有的无学习能力都是由大脑的不同构成方式导致的，所以C项的内容在文章中有提到了。第五段中作者讲到：盖茨维德医生指出，无学习能力主要是由于大脑左半部的问题造成的，所以D项也是文章中提到的内容。文中并没有提到未知部位的相关内容，所以A项不对。因此本题的正确答案为A。
单选题
All of the following statements are true EXCEPT that______.
【正确答案】
C
【答案解析】解析：文章在第一段中就提出了“Learning disabilities are very common．They affect perhaps 10 percent of all children．”无学习能力是一种非常普遍的现象。它们或许影响10％的儿童。可见无学习能力虽然是普遍现象，但它影响的仅可能是10％的儿童。所以C项的说法不符合文意。文章第二段“Scientists now know there are many different kinds of learning disabilities and that they are caused by many different things．”科学家认识到，无学习能力有许多不同的种类，并且它们是由许多不同的原因引起的。所以A项的叙述正确。第三段指出：无学习能力这种疾病没有外在标记，所以B项也正确。最后一段中讲到： “Doctor Duffy found large differences in the brain activity of normal children and those with reading problems．”达菲医生发现，正常儿童与无学习能力儿童的脑部活动有差异，可见D项也正确。所以本题的正确答案为C。