I believe the third stanza is the correct answer:
<span>Seven captains at our seven gates
Thundered; for each a champion waits,
Each left behind his armor bright,
Trophy for Zeus who turns the fight;
Save two alone, that ill-starred pair
One mother to one father bare,
Who lance in rest, one 'gainst the other
Drave, and both perished, brother slain by brother.
These lines tell the story of what happened immediately prior to the play Antigone. It describes the events of when her two brothers fought and kill each other in battle, which is the reason why the play Antigone exists. The first two stanzas describe events from a long time ago, and the fourth one are current events. The third one gives a background to the story, which is why I'd pick that option.
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There are a few that aren't really supposed to be used in formal writing. contractions, for example, are supposed to be written out--"don't" becomes "do not"--because contractions are something we vocally combined to make our speech a little lazier and flowy. this makes contractions a more "casual" part of speech. interjections aren't encouraged either, because we typically make interjections in casual speech; these don't go hand in hand with formality.
