Whichofthefollowingdevicescanrouteelectricalsignalsonlywhenactivatedbyanexternalcontrolsignal?() A.SolenoidB.RelayC.ClutchD.Capacitor

Whichofthefollowingdevicescanrouteelectricalsignalsonlywhenactivatedbyanexternalcontrolsignal?()

A.Solenoid

B.Relay