Was it the last one? Because I feel like it could be either the last two, but the each of them aren't exactly right. Isn't the climax when Creon realizes he needs to pardon Antigone and/or he finds that Antigone has hung herself? At the same time, the last answer says "The complicating incident of the play has been revealed", and it seems several complicating incidents have already been revealed (like Antigone trying to bury her brother) and the main conflict is Antigone's choice to disobey the Creon's edict and Creon's pride not letting her go, and it doesn't seem like the argument with Haimon is "the complicating incident" that made the conflict happen...maybe "one of the complicating incidents.