Electric cargo winches have an overload safety device which normally cuts the current to the winch motor（）.

A.after torque cause line pull to exceed the rated capacity of the winch

B.before the line pull reaches the rated capacity of the winch

C.when the line pull reaches the breaking strengh of the fall

D.before the safe working load of the fall is reached

空间力偶矩是（）。

A.代数量

B.滑动矢量

C.定位矢量

D.自由矢量