17._______yesterday, you would have met Professor Jones. But now he has left for London。A. Did you come B. Had you comeC. Should you come D. Were you to come应该选 b 虚拟 ...
这是表示过去情况的虚拟条件句如果你昨天过来的话，就能见到Jones教授了。他现在已经出发去伦敦了。原句相当于If you had come yesterday, you would have met Professor Jones. But now he has left for London.可省略if,采用倒装形式而把had提前，所以...
