If the Houses of Parliament had not been burned down in 1834
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.