We _____________ martial arts at the gym when we heard the news. [ ]

A. are playing

B. are doing

C. were playing

D. were doing

共用一套浮动杆控制的两台舵机主变量泵零位不一致，则同时使用时会（）。

A.滞舵

B.冲舵

C.跑舵

D.舵慢