Answer:
The answer is: The surfing vacation has functioned as an extrinsic motivator.
Step-by-step explanation:
Extrinsic motivation refers to a desire to perform a specific behavior in order to get something from it, like a reward, or to avoid something, like a punishment. Exstrinsic motivation comes from an external reinforcement.
In this case, Molly got straight A's on her report card because she wanted to go on the surfing vacation that her dad promised her if she got straight A's. Therefore, the surfing vacation serve as an extrinsic motivator.