Question

cue that signals that reinforcement is available if the subject makes a particular response
negative reinforcement
stimulus discrimination
primary reinforcer
secondary reinforcer
discriminative stimulus

Explanation:

A discriminative stimulus is a cue that signals the availability of reinforcement if a particular response is made. Negative reinforcement involves the removal of an aversive stimulus to increase a behavior. Stimulus discrimination is the ability to differentiate between stimuli. Primary and secondary reinforcers are types of reinforcers, not cues for reinforcement availability.

Answer:

E. discriminative stimulus