A．带正电
B．带负电
C．带正电或带负电不能确定
D．不带电
答案：D
三类泵中对油过滤的要求较低的是( )。
A．齿轮泵
B．叶片泵
C．柱塞泵
Point out which one of the following items is not in the charge of Chief Officer in repairing operation（）.
A.hull cleaning
B.derusting and painting
C.the maintenance of boiler
D.docking and undocking
