Answer: C) Allusion.
Explanation: an allusion is a literary device that consists in making a brief reference to a person, an event (historical, political, cultural, etc), or to a place. The given line from Martin Luther King’s “Letter from Birmingham Jail” is an example of an allusion, in this case, King is alluding to something that T. S. Eliot had said. So the correct answer is the corresponding to option C: allusion.
