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
单项选择题 If the engine of a survival craft does not start，check to see（）.
单项选择题 If a gasoline engine turns over freely but will not start，the cause is generally（）.
单项选择题 Each cylinder in a two stroke cycle engine experiences combustion（）.
