The reasearch question that best fits the claim and reason is
D. How does the lack of sleep hurt someone's health?
Both the claim and the reason have to do with the damage not sleeping enough can have on a person's health. Therefore, the research question needs to be related to that same topic. Even though the reason is that the person is less alert, focusing on this isn't related to the claim. Also, while it may be helpful to research what causes someone not to sleep well, it doesn't support the claim that not sleeping enought is bad for a person's health.
