A child learning to talk does not learn by being corrected all the time; if corrected too much, he will stop talking. He notices a thousand times a day the difference between the language he uses and the language those around him use. Bit by bit, he makes the necessary changes to make his language as other people"s.

单项选择题Few people have the time that is required to master a full knowledge of a foreign language and ______ still would be to make the much practical use of such a language.

单项选择题Most studies focus on remarkably precise slivers of human emotions. One study at Allegheny University in Pennsylvania found that the tendency for a person to throw dishes or slam doors when he is angry is 40 percent heritable, ______ the likelihood a person will yell in anger is only 28 percent heritable.