单项选择题
Fuel droplets injected into a diesel engine cylinder must have adequate penetration to （）
A.prolong the ignition delay period B.ensure the beginning of fuel injection C.thoroughly utilize the air charge D.allow controlled fuel combustion
单项选择题 The primary function of a fuel delivery check valve assembly is to（）
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（）
