（） is sometimes used for piston cooling since leaks into the crankcase would not cause problems.

（） fuel oils （） lubricating oils require treatment before passing to the engine.

A.Both；and
B.Neither；nor
C.Either；or
D.Both；or

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（） 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

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