单项选择题
The function of synchronous compensating machine is to（）
A.improve power factor B.reduce voltage oscillation C.increase the insulation of circuits D.eliminate regenerated magnetic fields
单项选择题 What is head tank in the closed cooling water system used for?（）
单项选择题 According to the principle of four stroke diesel engine, what is the number of its efficient work stroke per revolution?（）
单项选择题 What type of electric motor is most commonly used on board ship?（）
