Question

【题目】Only when class began ______ that he had left his book at home.

A. will he realizeB. he did realize

C. did he realizeD. should he realize

Answer 1

【答案】C

【解析】

考查倒装结构。当only等词谓语句首时，主句采用部分倒装，句意：直到上课开始时，他才意识到他已经把书丢在家里面了。结合语境可知此处描述的是过去的动作，故用过去时态，助动词用did，故选C。