I believe that the correct option is D) Ismene´s fearfulness highlights Antigone´s boldness.
They are both characters from "Oedipus Rex" and "Sofocles". They are the two daughters of Oedipus with Jocasta who also had two sons, Eteocles and Polynices.
After Oedipus stepped down as king of Thebes he gave the kingdom to his sons who agreed to alternate in the throne every year. But after the first year passed Eteocles refused to stepped down and that lead to a war between brothers wich ended up with the death of both brothers and the ascension to the throne of Creon. Who declare Polynices a traitor and forbid to buried the corpse.
Antigone violate the order and in an attempt of burying his brother got caught. On the other hand Ismene´s fearfulness not allow her to defy the state and become an outlaw. Ismene serves as a counterpart of Antigone, the first one is compassionate and rational while the other one is headstrong with no regards of the consequences.
In a sense, they are foils. While Antigone demonstrates power and control over her own fate, Ismene shows weakness and the inhability to take her life into her own hands. She gives in to the stronger wills around her.
Finally when king Creon order to kill Antigone by burrying her alive, Ismene said that she also have participated in the conspiracy although she had not.
I hope that the answer is correct and help you understand the why of the option given. If you have any doubt don´t hesitate to ask me, if I can I will help you. Greetings.