There are two factors which determine all individual’s intelligence. The first is the sort of brain he is born with. Human brains differ considerably, some being more 1 than others. But no matter how good a brain he has to begin with, all individual will have a low order of intelligence 2 he has opportunities to learn. So the second factor is what happens to the individual—the sort of 3 in which he is reared.
　　The importance of environment in determining all individual’s intelligence can be 4 by the case history of the identical twills, Peter and Mark. Being identical, the twins had identical brains at 5 . and their growth processes were the same. When the twins were three months old ,their parents died, and they were placed in 6 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 7 . He was read to as a child, sent to good schools, and given every opportunity to be 8 intellectually. This environmental difference continued until the twins were in their late teens, when they were given tests to measure their 9 . Mark’s LQ. was 125, twenty-five points-higher than the average and 10 forty points higher than his identical brother. Given equal opportunities, the twills, having identical brains, would have tested at roughly the same level.
[A] separate　　　　　[B] stimulated　　　　[C] smart
[D] unless　　　　　　[E] when　　　　　　　[F] fully
[G] birth　　　　　　 [H] improved　　　　　[I] environment
[J] clearly　　　　　 [K] demonstrated　　　[L] similar
[M] intelligence　　　[N] capable　　　　　 [O] college