Classical Conditioning and Operant Conditioning Are Two Types of Learning

Classical conditioning and operant conditioning are two types of learning described by behaviourists.A major difference between them is that:

A) classical conditioning deals almost exclusively with stimuli, whereas operant conditioning deals almost exclusively with responses.
B) classical conditioning deals almost exclusively with responses, whereas operant conditioning deals almost exclusively with stimuli.
C) classically conditioned responses are voluntary, whereas responses learned through operant conditioning are involuntary.
D) classically conditioned responses are involuntary, whereas responses learned through operant conditioning are voluntary.