What Happens in Operant Conditioning

What happens in operant conditioning

A)  An organism's response is influenced by the observation of others, who are called models. 
B)  Voluntary responses come to be controlled by their consequences. 
C)  An organism's tendency to give a response reappears after a period of time. 
D)  A stimulus acquires the capacity to evoke a response that was originally evoked by another stimulus.