—You were out when I dropped in at your house.—Oh Ifor a friend from England at the airpor

问题补充：

—You were out when I dropped in at your house.

—Oh,Ifor a friend from England at the airport.

A. was waiting

B. had waited

C. am waiting

D. have waited

答案：

(答案→)A. was waiting

B. had waited

C. am waiting

D. have waited

解析：过去进行时可表示过去某一时间正在进行的动作或存在的状态。答语中暗含了when you dropped in at my house。