Catalina ate a candy bar and then went on a fast-moving ride in an amusement park. She was sick to her stomach after the ride and now, Catalina cannot eat candy bars, because they make her nauseous. In this learned association, the candy bar serves as a(n) to Catalina.

A conditioned stimulus

Explanation:

 A conditioned stimulus is one of the type of classical conditioning process in which it basically explain about the various types of learning theory as it basically helps in determining the various types of response and also triggering the various types of conditioned response.

According to the given question, In the given learned association, the candy bar is basically serves in the form of a conditioned stimulus. The conditioned response is also known as the response triggering process.    

  Therefore, A conditioned stimulus is the correct answer.

it would be d). more resources must be obtained to attain that combination of goods and services