单选题

So  the  second  factor  is  what  _50_  to  the individual—the sort of environment in which he is brought _51_.

单选题 an individual will have a low order of intelligence  _49_  he  has  opportunities  to  learn.

单选题 Human brains differ considerably _47_, being more capable than others.

单选题 If an individual is handicapped (受阻碍）_52_,

单选题 _48_ no matter how good a brain he has to begin with

单选题  So  the  second  factor  is  what  _50_  to  the individual—the sort of environment in which he is brought _51_.

单选题 There are two factors which determine an individual's intelligence. The first is the sort of brain he is born _46_.

单选题 he will _54_ attain the level of intelligence of which he is _55_.

单选题 it is likely that his brain will _53_ to develop