What Is a Major Difference Between Operant Conditioning and Classical

What is a major difference between operant conditioning and classical conditioning?​

A) In operant conditioning, the learner's response controls what happens next.
B) Classical conditioning associates three events instead of two.​
C) Responses learned in operant conditioning are rapidly forgotten unless rehearsed often.​
D) Classical conditioning controls skeletal muscles; operant conditioning controls the viscera.​