听力原文: There are two factors which determine an individual's intelligence. The first is
The importance of environment in determining an individual's intelligence can be demonstrated by the case history of the identical twins, Peter and Mark. The twins had identical brain at birth. When the twins were three months old, their parents died, and they were placed in different 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 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 I. Q. was 125, twenty five points higher than the average and fully forty points higher than his identical brother.
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A.Human brains differ considerably.
B.The brain a person is born with is important in determining his intelligence.
C.An environmentally handicapped person won't attain his due level of intelligence.
D.Environment is important in determining a person's intelligence.