Answer:
The condtioned stimulus is the red flowers.
Explanation:
In classical conditining, a conditioned stimulus (the flowers) is associated with an unrelated consequence, called unconditioned stimulus (the sting). This produces a reaction known as conditioned response (fear).
It's important to acknowledge that any neutral stimulus can become conditioned. In this example, Marshall could have been afraid of yellow flowers, instead of red, if the incident had involved the former.
