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?
答
过去完成时，
答
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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