if he had only known he was building his own house,he would have done it all so differently.

问题描述:

if he had only known he was building his own house,he would have done it all so differently.
要按照语法的,字字翻译,

这是一句虚拟语气的句子表示假设的情况和过去发生的事实相反.也就是说“他不知道他建的是他自己的房子,所以建得不怎么样”.原句意思:
“如果当时他知道在建的是他自己的房子,他会把它建得与现在完全不同”