Answer:
The answer is neutral stimulus and conditioned stimulus, respectively.
Explanation:
In classical conditioning, a conditioned stimulus is associated with an unrelated consequence, called unconditioned stimulus. This produces a reaction known as conditioned response.
The passage illustrates the fact that any neutral stimulus can become conditioned, as long as it's paired with an unconditioned stimulus. For example, instead of a buzzer, the stimulus could have been a coloured light or a different sound. When associated with the puff of air, it would become conditioned.