Four years ago, Jared used to have many luggages when driving to see his girlfriend

Four years ago, Jared used to have many luggages when driving to see his girlfriend.   She always teased him that he was traveling "very heavy".  But now that he is studying in Australia, he has to take several planes to go see his girlfriend back in the States.  At first he continued carrying several suitcases with him, although it was laborious.  Now, he finally travels with only one suitcase. The fact that he no longer carries several pieces of luggage when traveling reflects a learning process called: 
Question 6 options:
operant conditioning -negative punishment
classical conditioning
operant conditioning -positive punishment
social learning
operant conditioning -negative reinforcement
operant conditioning -positive reinforcement