问题 选择题

   a bad habit is formed, it will take a long time to get rid of it.

A.Ever since

B.While

C.Once

D.Even if

答案

答案:C

考查连词的用法。句意:一旦坏习惯形成,它要花好长一段时间才能摆脱。Once 一旦。故选C。

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