—I called you at six o'clock yesterday evening but there was no reply.

—Oh, I'm sorry. I _______ dinner at my friend's. [ ]

A. was having

B. is having

C. had

D. have

后室是烘丝机的出料端，也是烟丝在烘筒内升温后蒸发出来的（）被热风带走的排放处。