Final answer:
In the play 'Agamemnon', Clytemnestra is helped by her cousin Aegisthus when she kills Agamemnon.
Correct option is a.
Step-by-step explanation:
In the play 'Agamemnon' by Aeschylus, the wife of Agamemnon, Clytemnestra, is helped by her lover Aegisthus when she kills Agamemnon. Aegisthus is portrayed as Agamemnon's cousin in the play.