In What Way Does Operant Conditioning Differ from Classical Conditioning

In what way does operant conditioning differ from classical conditioning?

A) In classical conditioning, learning is fastest during the early trials, while, in operant conditioning, learning is fastest during the later trials.
B) In classical conditioning, the consequence arrives regardless of the animal's behavior, while, in operant conditioning, it only arrives once the animal has made a response.
C) Classical conditioning can be used to train animals to make responses they would not normally make; operant conditioning cannot be used to do this.
D) Extinction occurs in classical conditioning but not in operant conditioning.