4.________ you recognize an idiom when it is being used，it is easy to misunderstand what you read or hear.

A.Although B.Because

C.Unless D.While

答案　C　[句意：除非你在一个习语得以使用时认识它，否则你就很容易误解你所读到的或听到的。根据句意，此处表示"如果不......，除非"，故要用unless。although "尽管"；because "因为"；while "当......时候"，均不符合句意。]

5.-Stephen Hawking devoted himself to scientific research before becoming one of the greatest physicists.

-That's it.________.

A.Two heads are better than one

B.One false move may lose the game

C.All things are difficult before they are easy

D.Champions are made when no one is watching

答案　D　[句意：--斯蒂芬·霍金在成为一位最伟大的物理学家之前致力于科学研究。--就是这样。十年寒窗无人问，一朝夺魁天下知。Two heads are better than one"两人智慧胜一人"；One false move may lose the game"一着不慎，满盘皆输"；All things are difficult before they are easy"万事开头难"；Champions are made when no one is watching"十年寒窗无人问，一朝夺魁天下知"。根据语境可知选D项。]

6.________ you try to do something beyond what you have already mastered，you will never grow.

A.Once B.If

C.Because D.Unless

答案　D　[句意：除非你努力做超出你掌握的事情，否则你永远不会成长。once意为"一旦"；if意为"如果"；because意为"因为"；unless意为"除非"。根据句