Every Time Luis Gives His Dog a Treat,he Shakes the Box

Every time Luis gives his dog a treat,he shakes the box of treats first.His dog now reacts excitedly to the sound of the box of treats being shaken,even before Luis takes out a treat.In this situation,the treat is the

A) unconditioned response.
B) conditioned response.
C) unconditioned stimulus.
D) conditioned stimulus.