单项选择题
A.Gas exchange B.Charging C.Scavenging D.Supercharging
（） is sometimes used for piston cooling since leaks int...
单项选择题（） is sometimes used for piston cooling since leaks into the crankcase would not cause problems.
A.Diesel oil B.Hydraulic oil C.Lube oil D.Mineral oil
（） fuel oils （） lubricating oils require treatment befo...
单项选择题（） fuel oils （） lubricating oils require treatment before passing to the engine.
A.Both；and B.Neither；nor C.Either；or D.Both；or
（） device is provided to prevent starting air from bein...
单项选择题（） device is provided to prevent starting air from being admitted to the cylinder before the reversing is completed.
A.An automatic B.A transmission C.A self-regulating D.An interlocking
