By the time the course ends,a lot _____ about the United States.

问题描述:

By the time the course ends,a lot _____ about the United States.
A.will have been learned B.will have learned
C.are learned D.have been learned
为什么不选D

应该是A.
a lot代指很多知识,所以用被动.
by加将来时,用将来完成时.
所以选A
意思是:到这个课程结束的时候,很多关于美国的知识将被学到(你将会学会很多关于美国的知识).