how long _______ he__________London before he came here?

问题描述:

how long _______ he__________London before he came here?

How long had he been in london before he came here?他来这里之前在伦敦呆了多久?从“before he came here”中的“came”可以看出句子所问的是“过去的过去”,而表达“过去的过去”的的时态是过去完成时“主语+had...