—You were out when I dropped in at your house yesterday.—Oh I for a friend from Beijing a

问题补充：

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

—Oh, I for a friend from Beijing at the railway station.

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：根据上句中的时间状语的提示可知谓语动词是指过去某时正在发生的事情，因此用过去进行时态，故答案为 A。