I was deep in thought so I didnt notice .A. him to come inB. him come inC. he come inD.

问题补充：

I was deep in thought, so I didn notice .

A. him to come in

B. him come in

C. he come in

D. him coming in

答案：

A. him to come in

B. him come in

C. he come in

(答案→)D. him coming in

解析：notice sb. doing更强调当时看见某人正在进行的动作。