Which of the following fits the description of a flat character?
a. the soldier maintains his love for his country despite losing several members of his squad in a battle
b. the taxi driver is a student at the most prestigious law school in the country during the day
c. the teacher allows some students to talk and chew gum during class but punishes other students for doing the same
d. the politician who supports environmental policies conspires with oil companies that want to drill in a nature preserve