Question

Only when he started to explain ________ the reason for this

Answer 1

1.Only when he started to explain（ did she realize ） the reason for this.

就在他开始解释的时候,她才明白其原因.

Only强调状语置于居首时,使用部分倒装,即把谓语的一部分（助动词、情态动词和系动词be）放到主语前.本句中 Only 强调时间状语when he started to explain,所以答案应选B.

2.After that we never saw her again nor（ did we hear ）from her.

从那以后,我们再也没见过她,也没有关于她的任何消息.

否定副词、连词neither,nor,never,hardly,scarcely,little等及含有否定词的介词短语,如in no time等置于句首时,使用部分倒装.

3.Scarcely （had I entered） the room（ when） the phone rang.

我一进房间电话铃就响了.

和上一题一样,scarcely放于句首句子使用部分倒装.另外,Hardly / Scarcely had sb.done sth.when...是固定结构.