Because his football coach frequently yells at him for swearing, antonio now becomes anxious when he's near his coach. the coach is a(n) for antonio's anxiety.
a. secondary reinforcer
b. conditioned stimulus
c. unconditioned stimulus
d. negative reinforcer

The coach is a B. conditioned stimulus for Antonio's anxiety.

Explanation:

In classical conditioning, a conditioned stimulus is a previously neutral stimulus who became as such by being paired with an unconditioned stimulus. It will activate a conditioned response in the future.

In this case, Antonio's coach has become a conditioned stimulus; his yelling was the unconditioned stimulus and Antonio's anxiety is his conditioned  response to this.