轴承根据相对表面运动表面的摩擦性质，轴承可分为（）。
A.滑动轴承
B.滚动轴承
C.推力轴承
参考答案：A, B
活塞环中，气环的作用是（）和（）。
The rule state that a vessel overtaking another vessel is relieved of her duty to keep clear when（）.
A.she is forward of the other vessel’s beam
B.the overtaking situation become crossing situation
C.She is past and clear of the other vessel
D.the other vessel is no longer in sight
