Bob is waiting outside.the come in,Mr.Yang?----Yes.invite him in.

问题描述:

Bob is waiting outside.the come in,Mr.Yang?----Yes.invite him in.
A May
B Can
C Shall
D Should

因为本句的时态为一般将来时(因为是将要让bob进来,还没有进行所以是一般将来时),而一般将来时一般的疑问句用助动词shall提问,所以选c