Question

He was told that it would be at least there more months ( ) he could recoveer and return to work.

A.when
B.before

为什么选B而不选A？

再问下，这个”when“和”before“填的时候怎么区分？

Answer 1

很简单，因为前面的three months是“3个月”。when是短暂性的”时间点“，很明显这里不是短时间。
而before可以接长的“时间"。
比较下面两句话。你就知道when和before的区别了：
It was 10 o'clock when the teacher came in the classroom.老师进教室的时候是10点钟。（时间点）
It was more than 10 hours before the teacher came in the classroom.老师进教室之前已经过了10个小时了。（时间段）