What you at 7 last night?
A. did , do B. were , do C. were , doing
What you at 7 last night?
A. did , do B. were , do C. were , doing
C
【解析】句意：昨天晚上7点你在做什么？did…do是一般过去时态的疑问句形式；were…do形式错误，be动词后面不跟动词原形；were…doing是过去进行时态，表示过去某个时间正在进行的动作。根据句意和句中的时间状语at 7 last night可知，这里表示过去的时间正在做的事情，应使用过去进行时态，故选C。