In classical conditioning, if the unconditioned stimulus is no longer being paired with the conditioned stimulus,

what will occur?

extinction

Explanation:

Extinction: In psychology, the term extinction is defined as the phenomenon in which a formerly learned behavior is being disappeared when that particular behavior is not being reinforced. It can happen in various behavioral conditioning including the classical conditioning yet mostly associated with the theory of operant conditioning.

In extinction, the conditioned response becomes gradually weak that leads to disappear or decrease a particular behavior.