Philosopher: Graham argues that since a person is truly happy only when doing something, the best life is a life that is full of activity. But we should not be persuaded by Graham's argument. People sleep, and at least sometimes when sleeping, they are truly happy, even though they are not doing anything.

Question: Which one of the following most accurately describes the role played in the philosopher's argument by the claim that at least sometimes when sleeping, people are truly happy, even though they are not doing anything?
Options:
A. It is a premise of Graham's argument.
B. It is an example intended to show that a premise of Graham's argument is false.
C. It is an analogy appealed to by Graham but that the philosopher rejects.
D. It is an example intended to disprove the conclusion of Graham's argument.
E. It is the main conclusion of the philosopher's argument.
Answer: "B"