Answer:
The conditioned response is when his ears pop when entering a building with an elevator.
Explanation:
The first times that Alex used the elevator there wasn't a conditioned response yet, using the elevator was the unconditioned stimulus and his ears popping was the unconditioned response. After using the elevator several times, the elevators (neutral stimulus) were associated with the unconditioned response until a moment when the neutral stimulus now triggered the unconditioned response; at this point the response is now a conditioned response.
Answer:
But what is your question
Explanation:
To fill in the blank the word needed is " play "
I'm honestly not 100% sure but you should try A.