In the Middle of a Difficult Exam, Sam Tells His

In the middle of a difficult exam, Sam tells his teacher that his stomach hurts, and the teacher immediately sends him to the school nurse, who lets Sam lie down and take a nap. Sam's teacher takes notice that on several later occasions when Sam has a difficult test or assignment, Sam again tells the teacher that he doesn't feel well. Each time the teacher sends him to the school nurse without completing his work, and without being penalized. Sam is being:

A) positively reinforced.
B) punished.
C) subjected to observational learning.
D) negatively reinforced.