单项选择题
While engine is in operation the piston moves up and down, thus causing the rotation of the （）.
A.crankcase B.slipper C.cam housing D.crankshaft
单项选择题 Which of the following would cause a diesel to have black smoke?（）
单项选择题 Which of the following will take place if the clearance of the main bearings are excessive?（）
单项选择题 Which of the following will be the function of lubricating oil used in marine engines?（）
