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