Dr. jones 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. jones closes the classroom door. closing the door has become a(n) stimulus.

The correct answer is a conditioned stimulus.

A conditioned stimulus (CS) refers to a previously neutral stimulus, that when repeatedly paired with an unconditioned stimulus (UCS) elicits the same response as the UCS, even in the absence of the UCS. In this example, the CS is Dr.Jones closing the classroom door, because this stimulus by itself elicits a response of anxiety in students.