Marginal Thinking Is Best Demonstrated By

Marginal thinking is best demonstrated by:

A) 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.
B) deciding to never purchase a coat made with animal skins or furs
C) acquiring the information relevant to a choice before making that choice
D) measuring all of the costs of a meal against all of the benefits when deciding whether to order a second milkshake