They ——about eight hundred English words by the end of last termA.have learned B.had learned为什么选B?

问题描述:

They ——about eight hundred English words by the end of last term
A.have learned B.had learned为什么选B?

过去完成时,

B.had learned
by + 过去某一时点 要和过去完成时连用
因为by 意为“不迟于”“在...之前”"到.时候”
by the end of last term 到上个学期末,所指的时间为【过去的过去】,所以要和【过去完成时】连用
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