Someone is at the door. must be Mr Smith.A. HeB. ItC. ThisD. That

问题补充：

Someone is at the door. must be Mr Smith.

A. He

B. It

C. This

D. That

答案：

A. He

(答案→)B. It

C. This

D. That

解析：考查人称代词。当没有指名性别时，指人用it。句意“有人在门口，他一定是史密斯先生。”故选B。