An accidental path of low resistance, allowing passage of abnormal amount of current is known as a/an（）.

A.Contactors control current and relays control voltage
B.A relay is series connected and a contactor is parallel connected
C.Contactors can handle heavier loads than relays
D.Contactors are made from silver and relays are made from copper

A.short proof
B.ground proof
C.explosion proof
D.overload proof

A.prime mover speed
B.exciter output voltage
C.load on the alternator
D.number of poles