单项选择题
DC generators are classified according to the manner in which（）
A.they are used B.the field windings are connected to the load C.the armature circuit is connected to the load D.the field windings are connected to the armature circuit
单项选择题 A circuit that has one wire in contact with the hull of the ship is a（）
单项选择题 If two AC generators are to be operated in parallel, the load is distributed evenly by（）
单项选择题 If a voltmeter is connected across a line, it must be protected with a（）
