Answer:
A) neutral stimulus
Step-by-step explanation:
A Russian physiologist proposed the mechanism of learning through association.
This process of learning involves the association of two or more stimuli to produce a new type of learning or response and John Watson named this mechanism as Classical conditioning.
The classical conditioning occurs in three stages: Before, during and after conditioning. In before conditioning, there is a stimulus which does not produce response but with an unconditioned response produces a response called the neutral stimulus.
Thus, a neutral stimulus is the correct answer.