单项选择题 An ohmmeter can be used to measure（）

单项选择题 The instantaneous reduction in voltage of an AC generator, resulting from an increase in load, and prior to the automatic voltage regulator correcting the situation, is called voltage （）.

单项选择题 If both the “high level” and “low level” alarms come on for the same address of a centralized control console, the most likely problem is a/an （）.