单项选择题

Passage 2
There are two aspects which determine an individual’s intelligence. The first is the brain he is born (71) Human brains differ considerably, (72) being more able than others. (73) no matter how good a brain he has to begin with, an individual will have a low order of intelligence (74) he has opportunities to learn. So the second aspect is what (75) to the individual — the environment in which he is brought (76) . If an individual is handicapped (77) , it is likely that his brain will (78) to develop and he will (79) attain the level of intelligence of which he is (80) .

72（）

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