The frequency of an AC generator is controlled by the （）

A.current in the circuit
B.voltage in the circuit
C.inductance in the circuit
D.resistance in the circuit

A.opposes any change in the applied voltage
B.opposes any change in the current flow through the circuit
C.aids any changes in the applied voltage
D.aids any changes in the current through the circuit

A.low loads necessitate frequent insulation cleaning
B.exceeding nameplate values shortens useful life
C.energy is wasted if full loading is not utilized
D.power factor correction methods are load dependent