Final answer:
Behavioral psychotherapists using classical conditioning are likely to use systematic desensitization, which pairs a relaxed state with an anxiety-inducing stimulus to extinguish the fear response.
Step-by-step explanation:
A behavioral psychotherapist who uses a technique based on classical conditioning is most likely to employ systematic desensitization with her client. In systematic desensitization, a client is gradually exposed to the fear-inducing object or situation under relaxed conditions until the fear response is extinguished. This technique is rooted in classical conditioning because it involves pairing a relaxed state with the anxiety-producing stimulus until the stimulus no longer elicits the anxious response.
Operant conditioning, on the other hand, involves modifying behavior through the consequences of that behavior, such as rewards or punishments. The major difference with classical conditioning is that operant conditioning focuses on voluntary behavior, while classical conditioning focuses on involuntary, reflexive behavior.