Answer:
The correct answer is option C. "historical allusion".
Step-by-step explanation:
A historical allusion refers to a brief and indirect reference to an historical event. If a play makes a reference about the assassination of Robert Kennedy, it would be an historical allusion of the tragic event of 1968. Historical allusion helps the audience to put in the context of the period of time that a play is set or to justify the events that take place in the play.