Answer:
Spontaneous recovery
Explanation:
Spontaneous recovery is a term that is used in operant conditioning. It is associated with the process of conditioning and learning. It is defined as the reappearance of the response after extinguished. The recovery of the response occurs without exposure to the stimulus. It is an instant recovery of the response. The response could occur from nowhere.
So that in the above statement, Greg an individual who smoked usually with friends but left smoking. But whenever he went with his friends in a bar, he urges strongly to light up a cigarette that is the example of spontaneous recovery.