When ____to compare the education systems of China and German,the professor gave no comment.

问题描述:

When ____to compare the education systems of China and German,the professor gave no comment.
a.asked him b.asked c.being asked d.asking him
请问应该选哪个 请讲一下原因

选B 因为 when 后面省略了he was ,这是把时间状语从句简化为过去分词短语作状语.语法是:句子并不是越复杂越好,如果在一个句子中有多个从句,会使人发晕,所以应尽量简洁,简单的方法之一就是把从句改为现在分词短语(...