Gracie helps her mother set the table for dinner without being asked. She lays out napkins and silverware, places the plates in their correct spots, and puts ice in all of the glasses. When her mother realizes that she has done this, she gives Gracie a big hug, thanks her repeatedly, and later gives her a little extra dessert as a treat. In learning theory, we would say that Gracie's behavior has

been:

a. punished.
b. extinguished.
c. reinforced.
d. differentiated.

c