292.When things don't turn out as we would like them to, it is very tempting to assume that had we done things differently, the story would have had a happier ending.
本句的主干是...it is very tempting...o when引导的是时间状语从句，该从句中又包含一个as引导的状语从句；that引导的是带有虚拟语气的宾语从句that had we done...a happier ending，作assume的宾语。Had we done things differently属于省略连词if后引起的倒装情况，还原后应为：if we had done things differently。
We shouldn't assume anything in this case.
Scientists assume there is animal life on Mars.
He assumed a look of surprise when I told him the story.
Nada said he would assume responsibility for his mistake.
The young man assumed the role of leader in the emergency.
My friend assumed a new name after he moved here.