Ever since she foolishly drank too much beer at a rock concert and vomited all over her boyfriend, Sharon becomes nauseated at the smell or taste of beer. In this example, the conditioned stimulus is and the conditioned response is .

the smell or taste of tequila; nausea

Explanation:

In classical conditioning, the conditioned stimulus is a previously neutral stimulus that initially, do not elicit a response until after being paired with a natural stimulus to elicit same response, while the response that is now being elicited by the previously neutral stimulus, is the conditioned response.

From the question above, we can infer that the smell or taste of tequila, ordinary will not cause nausea, is the previously neutral stimulus (conditioned stimulus) that has now become associated with a natural stimulus or unconditioned stimulus, which is drinking heavily. Drinking heavily,  is an unconditioned stimulus that can naturally elicit vomiting, which is an unconditioned response. The nausea caused by the smell or taste of tequila is referred to as the conditioned response.

The conditioned stimulus is the smell or taste of tequila, and the conditioned response is the nausea.