5.中文：他们问发生什么事了。

　　（误）They asked what happened.

　　（正）They asked what had happened.（主句是一般过去时，从句的动作发生在它之前，用过去完成时。）

6.中文：从战争开始时他就一直在那里工作。

　　（误）He has worked there since the war has begun.

　　（正）He has worked there since the war began.（since引导的从句表示过去的某时间点，应用一般过去时。）

7.中文：昨晚我写了一封信，今晨寄出了。

　　（误）I was writing a letter yesterday evening and posted it this morning.

　　（正）I wrote a letter yesterday evening and posted it this morning.（进行时表示进行，一般过去时表示完成，所以应用 wrote.）

8.中文：他去年离开家我就一直没有见过他。

　　（误）He left home last year and I did not see him since.

　　（正）He left home last year and I haven't seen him since.（since后面省去的是he left home last year，前面的句子要用完成时。）