Answer: D. A brief or indirect reference to a well-known person, character, or of it.
Step-by-step explanation:
to allude to something is to refer casually or indirectly to something. To contain a casual or indirect reference. Therefore, if you make an allusion you are making a passing or casual reference; an incidental mention of something, either directly or by implication
example: "The novels title is an allusion to Shakespeare."
in other words, the title of that particular novel is alluding to something Shakesperian.