Answer:
The correct option is A. Marginal thinking is best demonstrated by 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.
Explanation:
Marginal thinking can be described as a form of thinking in which a person evaluates the costs as well as the benefits of doing an extra task. The person thinks about the worth of the extra resources. For example, in the option A the person is thinking to study economics at the cost of an extra hour. This cost would benefit him to score more in the quiz which is worth the cost.