You Need to Buy a Gift for a Young Cousin's

You need to buy a gift for a young cousin's birthday.You go to the mall and see a girl wearing a Hello Kitty t-shirt.You remember there is a store in the mall with a lot of Hello Kitty merchandise so you go there and buy a little backpack.When you give it to your cousin,she is very excited.In terms of behavioral learning,seeing the girl with the Hello Kitty t-shirt was a __________.

A) drive
B) reinforcement
C) cue
D) response
E) prompt