( )the end of next month they will have finished the work.请写出原因

问题描述:

( )the end of next month they will have finished the work.
请写出原因

By...
在下个月月底之前。。。。他们会完成他们的工作。。。
by...在。。。之前(期限)

By the end of next month they will have finished the work.
下个月底前,他们就会完成工作了~
by+时间 ...之前

By
by the end of next month到下个月末

by
在下个月末之前
in the end 结构不对
at the end of只表示在月末