Henry Received a Bad Sunburn on His Face When He

Multiple Choice

Henry received a bad sunburn on his face when he was skiing last winter.Now,before he starts a day of skiing,he uses a sunscreen on his face to prevent another sunburn.In this case,avoiding a sunburn functions as

A) a negative reinforcer for using a sunscreen.
B) a positive reinforcer for using a sunscreen.
C) a conditioned stimulus for using a sunscreen.
D) an unconditioned stimulus for using a sunscreen.