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The importance of environment in determining an individuals 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 raised 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. Marks I. Q. 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. 21. This selection can best be titled____________. A. Measuring Your Intelligence B. Intelligence and Environment C. The Case of Peter and Mark D. How the Brain Influences Intelligence 22. The best statement of the main idea of this passage is that _______. A. human brains differ considerably B. the brain a person is born with is important in determining his intelligence | 
