Which of the Following Demonstrates Marginal Thinking

Multiple Choice

Which of the following demonstrates marginal thinking?

A) Deciding to never eat meat.
B) Deciding to spend one more hour studying economics tonight because you think the improvement on your next text will be large enough to make it worthwhile to you.
C) Deciding to go to a Sociology class that you usually skip because there is a guest lecturer you are really interested in hearing that day.
D) Both b. and c. demonstrate marginal thinking.