They ____ 3000 English words by the end of next month.

问题描述:

They ____ 3000 English words by the end of next month.
A.learned B.had learned C.will learn D.have learned
by the end不是加过去完成时吗?这边为什么选C

next month 不是将来时么?
既然是将来时,那符合选项的只有C
或者填写 will have learned也正确