What lesson did Robert Wood learn from his graduate school professor, leading to what we are calling the "Wood Principle"?

A. The first thing you must do in approaching a disagreement is to clearly determine which side is "right" and which side is "wrong."
B. Before you criticize an idea, you must learn how to state it in the strongest possible way.
C. If you want to persuade people of your position, you should focus on the weakest element of any argument you oppose.
D. The goal of any disagreement is to convince someone that your position is the right one.