Daniel Decides to Spend the Last Two Hours of the Night

Daniel decides to spend the last two hours of the night before his economics exam studying instead of sleeping. For Daniel, what would his tradeoff be?

A) nothing, since no dollar value can be put on sleep
B) nothing, since studying would be more beneficial than sleep
C) the six hours of sleep he could have had if he had gone to bed before midnight
D) the two hours of rest he would have gotten