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.

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.