时间状语从句 I had been looking for this kind of herb for two months ___ I found it at last.

分类: 作业答案 • 2022-01-09 18:03:57

问题描述：

时间状语从句 I had been looking for this kind of herb for two months ___ I found it at last.
选before,为什么不是when呢?

答

Before+I found it at last.构成了一个时间段,即“我发现它之前”这一段时间；既然是时间段,所以要用完成时态,跟前半句相符；表示“我发现它之前一直在做某事”；
when+I found it at last.是“我发现它的时候”,构成了一个时间点,应该接过去时；