Mike didn’t notice Alice entering his room. He a phone call.A. answeredB. has answeredC.

问题补充：

Mike didn’t notice Alice entering his room. He a phone call.

A. answered

B. has answered

C. was answering

D. is answering

答案：

A. answered

B. has answered

(答案→)C. was answering

D. is answering

解析：本句的语义环境为：He a phone call when Alice entered his room表示过去某一时间正在发生.进行的动作，用过去进行时。故选C