Dr. Garcia is known for his difficult pop quizzes. Immediately before he springs a pop quiz on his students, he typically goes to the classroom door and closes it, and his students begin to feel anxious and tense. Students soon learn to anticipate a pop quiz and feel anxious whenever Dr. Garcia closes the classroom door. Closing the door has become a(n) .

The answer is conditioned stimulus.

Explanation:

In classical conditioning, a conditioned stimulus (closing the door) is associated with an unrelated consequence, called unconditioned stimulus (the pop quizzes). This produces a reaction known as conditioned response (anxiety).

It's important to recognise that any stimulus can become conditioned. For example, Dr. Garcia could slam his books on the desk instead of closing the door, and it would produce the same reaction when paired with the unconditioned stimulus.

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