Lucas Works at a Drive-Thru

Multiple Choice

Lucas works at a drive-thru.Every time the window opens,he hears an audible 'click' followed by a blast of freezing cold air.One day his window is stuck,and it gives the 'click' sound but doesn't open.Lucas finds himself shivering to the sound of the 'click' alone.In this example,the 'click' is the

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