单项选择题

In nautical terminology a dog is a（）.

A.crow bar
B.device to force a water tight door against the frame
C.heavy steel beam
D.wedge

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单项选择题

A.that the fuel valve is open
B.if the air supply system is open
C.if the water sprinkler system is open
D.if the limit switch is on

单项选择题

A.a defective ignition system
B.low lube oil level
C.weak valve springs
D.too heavy a load

单项选择题

A.once each crankshaft revolution
B.twice each crankshaft revolution
C.every other crankshaft revolution
D.every fourth stroke