Did you know what ( ) in twenty years?A,will happen B.would happen C.had happened选哪个,原因是?

Did you know what ( ) in twenty years?A,will happen B.would happen C.had happened选哪个,原因是?
Did you know what ( ) in twenty years?A,will happen B.would happen C.had happened选哪个,原因是?

Did you know what ( ) in twenty years?A,will happen B.would happen C.had happened选哪个,原因是?
B
in twenty years是二十年以后的意思,所以应该是将来时态,排除C,C是过去完成时态
然后,问句是用Did开头,是过去式,后面的从句也要是相应的过去式.所以用过去将来时,would happen

b
译为：你知道今后二十年会发生什么事吗？
因此c不行，完成式表示过去发生的事持续或影响到现在，用在表示将来中不合适
因did you know 可知这是过去时，所以a排除，选B