Answer:
The UCS (Unconditioned Stimulus) in this example is the wet cat food that the cat gets every other day. The cat is naturally excited and stimulated by the smell and taste of the wet cat food, which is an unconditioned response. The electric can opener is a neutral stimulus that has become associated with the presentation of the wet cat food and has become a conditioned stimulus that elicits the conditioned response of excitement and anticipation in the cat. In the case of Tabetha's mother opening a can of tuna, the cat is still responding to the sound of the electric can opener as a conditioned stimulus that has become associated with the unconditioned stimulus of wet cat food.