单项选择题
The lube oil to lubricate the surfaces of the cylinder liners is spread over by the （）.
A.sliding piston rings B.engines camshaft C.small pumps D.forced feed system
单项选择题 The most important factor that causes the wear of the engine parts is （）.
单项选择题 In the closed cooling system, the water （）.
单项选择题 If the temperature drops low enough, oil will not flow, （） just tell us the temperature.
