The correct answer is C. an allusion.
When you refer to something in a particular text that doesn't actually appear in that text, or when you imply the reference to something, it means that you are alluding to that particular something - you are making an allusion to that. Point of view is just about who tells the story; theme is the topic of the story; a symbol is the metaphorical way to refer to something in a story, but not an actual reference.
