单项选择题
The primary function of a fuel delivery check valve assembly is to（）
A.deliver proper fuel quantity to the injection nozzle B.provide rapid fuel injection cutoff C.control fuel quantity entering the pump body D.control fuel pressure delivered to the combustion chamber
单项选择题 For any piston ring to operate smoothly without scuffing ,the ring must be （）.
单项选择题 Shaker, circulation and spray are the three general methods used in（）
单项选择题 Wristpin bearings are difficult to lubricate because of their oscillating motion and（）
