单项选择题
（）is not installed on the main switchboard.
A.Ammeter and changeover switch B.Power factor meter C.Synchroscope D.Reverse sequence relay
单项选择题 （）is used to control, modulate, monitor and protect generator set.
单项选择题 （）is not a part of the main switchboard.
单项选择题 （）is not a part of the main switch board.
