B

　　There are two factors which determine an individual’ s intelligence. The first is the sort of brain he is born with. Human brains differ considerably, some being more capable than others. But no matter how good a brain he has to begin with, an individual will have a low order of intelligence unless he has opportunities to learn. So that second factor is what happens to the individual, the sort of environment in which lie is reared. If an individual is handicapped environmentally, it is likely that his brain will fail to develop and he will never attain the level of intelligence of which he is capable.

　　The importance of environment in determining an individual’ s intelligence can be demonstrated by the case history of the identical twins, Peter and Mark. Being identical, the twins had identical brains at birth, and their growth processes were the same. When the twins were three months old, their parents died, and they were placed in separate foster homes. Peter was reared by parents of low intelligence in an isolated community with poor educational opportunities. Mark was reared in the home of well - to - do parents who had been to college. He was read to as a child, sent to good schools, and given every opportunity to be stimulated intellectually. This environmental difference continued until the twins were in their late teens, when they were given tests to measure their intelligence. Mark’s IQ was 125, twenty- five points higher than the average and fully forty points higher than his identical brother. Given equal opportunities, the twins, having identical brains, would have tested at roughly the same level.

　　56. The best title for this passage is: ______.

　　A. Intelligence and Environment

　　B. How Someone’s Brain Has an Effect on His Intelligence

　　C. The Case of the Twins, Peter and Mark

　　D. Measuring Your Intelligence

　　57. The underlined sentence “The importance of environment in determining an individual’ s intelligence can be demonstrated by the case history of the identical twins” means that ______.

　　A. the environment one lives in has no effects on intelligence

　　B. one’s intelligence can have an important effect on the environment

　　C. the good environment one lives in has a bad effect on intelligence

　　D. whether the environment one lives in is good or bad has an important effect on intelligence

　　58. The best statement of the main idea of the passage is that ______.

　　A. human brains differ considerably

　　B. the brain a person is born with is important in determining his intelligence

　　C. environment is more important in determining a person’s intelligence

　　D. identical brains will have the same intelligence

　　59. According to the passage, the average IQ is ______.

　　A. 85 B. 100

　　C. 110 D. 125

　　60. This passage suggests that an individual’s IQ ______.

　　A. can be predicted at birth

　　B. stays the same throughout his life

　　C. can be increased by education

　　D. is determined by his childhood