Which of the Following Best Demonstrates Marginal Thinking

Which of the following best demonstrates marginal thinking?

A) measuring all of the costs of a meal against all of the benefits when deciding whether to order a second milkshake
B) choosing to spend one more hour studying economics because you think the improvement in your score on the next quiz will be worth the sacrifice of time
C) acquiring the information relevant to a choice before making that choice
D) deciding to never purchase a coat made with animal skins or furs