It is C. It was the only surviving trilogy. Aeschylus is called the father of tragedy because he made the plays Agamemnon, The libation bearers, and The furies. This trilogy ( called the Oresteia trilogy) is one of the most famous trilogies in Greek history. That is why Aeschylus's plays are still performed today. They have survived throughout the years.
Ps: I just learned this yesterday in my theater arts class.
