What is one major difference between operant conditioning and classical conditioning?

a)Operant conditioning takes place as a result of some voluntary action, while classical conditioning takes place without choice.
b)Operant conditioning takes place before the response, while classical conditioning takes place after the response.
c)Operant conditioning has both a stimulus and response while classical conditioning has a stimulus but not response.
d)Operant conditioning is learned by association, while classical conditioning is learned by reinforcement.