97免费在线观看视频,亚洲综合自拍网,黄色毛片免费观看,热久久综合网,免费看日产一区二区三区 狠狠操av,久久久涩涩涩,在线精品免费视频,人人插天天干,久久91精品国产91久久

單項選擇題

The main function of the lubrication system in to enable () of a film of oil between the moving parts.

A.the information
B.the formation
C.the scatter
D.the friction

微信掃碼免費搜題