The answer is D: How the protagonist overcomes his or her obstacles.
The protagonist, or main character, in a story is usually the key component to interpret any literary story. How a protagonist faces obstacles and overcomes them, or even fails to overcome them, is the best way to understand any cultural formation at any given time or moment in history; that is to say, it is the best way to comprehend what the protagonist´s culture (even if purely fictional) deems relevant, valuable, and desirable.