When someone is knocking at the door,you may ask"______"?

问题描述:

When someone is knocking at the door,you may ask"______"?
A.Who are you
B.Who it is
C.What are you
D.Who is it

应该是D
因为在问敲门的人的时候同打电话一样都不可以用Who are you 或What you are
所以AC不可能
即然这是一个特殊疑问句,那么就是由特殊疑问词和一般疑问句组成
所以只能选D