If the Houses of Parliament had not been burned down in 1834, the great clock would never have been erected.
问题描述：
If the Houses of Parliament had not been burned down in 1834, the great clock would never have been erected.
这句句子为什么从句用过去完成?
不是不真实的逐句用would家动词原形,从句用过去时吗?
为什么不是 If the Houses of Parliament was burned down in 1834, the great clock would be erected.
答
因为if 从句,would 所虚拟的事情发生在过去,主句应该用would have done,从句应该用had done .
如果是would be的话可以表示现在,将来的虚拟.
在牢记句子使用方法的时候要结合时态.