ZDl05型脉流牵引电动机抱轴轴瓦方孔上开有（）回油沟。
A、1条；
B、2条；
C、3条；
D、4条
参考答案：D
— I think it's going to be a big problem.
— Yes, it could be.
— I wonder _____ we can do about it. [ ]
A. if
B. how
C. what
D. that
何为脱模？
