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 researches did not examine brain tissue. Instead, they measured the brain's electrical activity and made a man of the electrical signals.
Frank Duffy experimented with this techniques at Children's Hospital Medical Center in Boston. Doctor Duffy said his research is evidence that reading disabilities involve damage to wide area of the brain, not just the left side.

单选题 Scientist found that the brain cells of a learning-disabled person differ from those of a normal person in ______.
A. structure and function
B. color and function
C. size and arrangement
D. color and arrangement

单选题 Which of the following is NOT mentioned in the passage?
A. Learning disabilities may result from the unknown area of the brain.
B. Learning disabilities may result from damage to a wide area of the brain.
C. Learning disabilities may result from abnormal organization of brain cells.
D. Learning disabilities may result from problems in the left side of the brain.

单选题 All of the following statements are true EXCEPT that ______.
A. many factors account for learning disorder
B. a learning-disabled person shows no outward signs
C. reading disabilities are a common problem that affects 10 percent of the population
D. the brain activity of learning-disabled children is different from that of normal children

单选题 Doctor Duffy believed that ______.
A. he found the exact cause of learning disabilities
B. the problem of learning disabilities was not limited to the left side of the brain
C. the problem of learning disabilities resulted from the left side of the brain
D. the problem of learning disabilities did not lie in the left side of the brain

单选题 According to the passage we can conclude that further researches should be made ______.
A. to investigate possible influences on brain development and organization
B. to study how children learn to read and write, and use numbers
C. to help learning-disabled children to develop their intelligence
D. to explore how the left side of the brain functions in language learning