Answer:
Tongue clicking is A. conditioned stimulus.
Explanation:
When it comes to classical conditioning, we can define a conditioned stimulus as a neutral stimulus that has become associated with an unconditioned stimulus and, eventually, begins to trigger a conditioned response. Tongue clicking was neutral; it did not cause any reaction in Francis. However, tongue clicking became associated with tickling. Tickling does cause Francis to squirm and giggle. Later, even if tickling is not happening, just the tongue clicking is enough to trigger the conditioned response of squirming and giggling. Therefore, tongue clicking is the conditioned stimulus.
B. nuclear weapons development
