Answer:
The correct answer is A
Explanation:
Facing a decision for yes or not (buy or not to buy, sleep or not to sleep, eat or not to eat, and so on) you will choose to do something if this something gives you a positive marginal benefit.
In this case your situation has two sides. By one side, watching an extra episode is good and gives you utility, buy you also need to study and not tu study gives you disutilty (or it's a cost). So, you will watch your episode if it gives you more marginal benefit than the cost it gives you.
If you are in a situation where the marginal cost and benefit are already equal you won't watch another episode, as the marginal benefit will be negative.
Watching an extra episode is not free, it has an opportunity cost (study for the exam)
And about D, watching an extra episode will not always guarantee fun, think about watching 18 episodes in a row, not going to school and getting fired from job.
So, correct answer: A
