I think it’s A but I’m not sure.

Which sentence is most clearly a topic sentence in a body paragraph from an essay?

A. One character in the novel must decide between living a traditional
life and changing his ways.
B. In the end, the author's description of these three characters
teaches an important lesson.
C. As the evidence has shown, the three characters support the
novel's theme about change.
D. Through the three characters in the novel, the author shows the
dangers of refusing to change.