Respuesta :
The correct answer is A. Conditioned stimulus
Explanation:
In classical conditioning, a conditioned stimulus occurs when a previously neutral stimulus begins to be associated with a specific response that has been reinforced or learned. For example, in the case of Pavlov experiment, the bell was initially a neutral stimulus as its sound did not trigger salivation in the dog; however, as Pavlov rang the bell along with food, the bell became a conditioned stimulus, because as any stimulus it leads to a response (salivation) but this is not natural but conditioned. Thus, the bell in this experiment had become a conditioned stimulus.