单项选择题
The connecting rod large end bearing shell generally has tags for location and oil grooves round the center of its axial length which correspond with grooves in the （） through which oil is transmitted up the rod to lubricate the small end.
A.connecting rod B.piston rod C.bearing housing D.none of the above
单项选择题 The conclusion that mechanical efficiency is always （） 100 percent is correct.
单项选择题 The compressed air is supplied by （） to the air reservoirs.
单项选择题 The compressed air is admitted to each cylinder through a cam operated by starting air valve when the piston has just passed its （）.
