You Are Driving to School When Suddenly an Ambulance Rushes

You are driving to school when suddenly an ambulance rushes past you with its sirens blaring,so you quickly pull your car to the side of the road.A few minutes later,when you hear sirens in the distance,you get ready to quickly pull the car over again.You have learned to respond quickly to the sirens because of

A) vicarious conditioning.
B) operant conditioning.
C) sensitization.
D) habituation.