Penny Recently Had a Root Canal at Her Dentist's Office

Penny recently had a root canal at her dentist's office. The procedure was more painful than she anticipated. She now needs to see a foot doctor in the same building, but when she arrives she feels a bit shaky as a result of the painful root canal. In this example, her fearful response to the pain of the root canal was a(n)

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