Deci Discovered That If You Are Rewarded for Performing a Fun

Deci discovered that if you are rewarded for performing a fun and interesting puzzle:

A) the puzzle becomes easier to solve than if you are not rewarded.
B) the puzzle becomes harder to solve than if you are not rewarded.
C) you become less likely to play with it later, when you are not rewarded.
D) you grow more likely to play with it later, when you are not rewarded.