_________ is hard is to do well all one’s life and never do anything bad．
A.He
B.It
C.That
D.What
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D解析句首的What is hard是主语从句，注意What is hard后的谓语动词is，假若没有后面的is，则应选B，即说成：It is hard to do well all one’s life and never do anything bad．C项作连接词时在句中没有意义。A项在句中不符的原因是hard不是he本身的特征。