An event that decreases the frequency of the behavior that it follows is a

A) negative reinforcer.
B) punishment.
C) conditioned stimulus.
D) secondary reinforcer.

A punishment is an event that decreases the frequency of the behavior that it follows. A negative reinforcer increases the likelihood of a behavior by removing an aversive stimulus, while a conditioned stimulus is a previously neutral stimulus that comes to elicit a response after being paired with an unconditioned stimulus. A secondary reinforcer is a stimulus that gains reinforcing properties through its association with a primary reinforcer.