What is a key difference between a theme and a central idea? a. a central idea is specific to a genre, such as epic poetry, while a theme is specific to a medium, such as written text. b. a central idea is relatively neutral, while a theme makes some kind of moral point. c. a central idea is a concept that a written work suggests, while a theme is a concept that a work states directly. d. a theme is revealed by characterization or plot, while a central idea is revealed by rhetoric or a direct statement. update: answer is d.