What makes one person more intelligent than another? What makes one person a genius, like the brilliant Albert Einstein, and another person a fool? Are people born intelligent or stupid, or is intelligence the result of where and how you live? These are very old questions and the answers to them are still not clear.
We know, however, that just being born with a good mind is not enough. In some ways, the mind is like a leg or an arm muscle. It needs exercise. Mental (done with the mind) exercise is particularly important for young children. Many child psychologists (心理 学家) think that parents should play with their children more often and give them problems to think about. The children are then more likely to grow up bright and intelligent. If, on the other hand, children are left alone a great deal with nothing to do, they are more likely to become dull and unintelligent.
Parents should also be careful with what they say to young children. According to some psychologists, if parents are always telling a child that he or she is a fool or an idiot, then the child is more likely to keep doing silly and foolish things. So it is probably better for parents to say very positive (helpful) things to their children, such as "That was a very clever thing you did." or "You are such a smart child.
According to the context we can guess that a genius is ______ while an idiot is ______.

A.a normal person; a funny person

B.a strong person; a weak person

C.a highly intelligent person; a foolish or weak-minded person

D.a famous person; an ordinary person