The correct answer is "Well, go, sir, and , whatever may occur, do what you concieve to be your duty."
From the story <em>"A Horseman in the Sky" </em>by Ambrose Bierce, the aforementioned quote is what determines Carter's behaviour throughout his encounter with the horseman, but it only takes full effect once the horseman faces his direction, revealing his identity to Carter, but not to the reader. At the end of the story, it is revealed that the horseman is in fact Carter Druse's father, and so it is proven that both Carter and his father were in opposite sides of a war.
This revelation causes Carter to shoot the horse of his father, implying he didn't have the nerve to kill his own father, but at the same time, attempting to live to his father's counsel: <em>"Do what you concieve to be your duty".</em>
The rest of the option cannot be correct since:
The second quote explains on of the story's facts, but one that does not have much impact on the plot, given that the horseman's actions (besides from his glance over Carter's position) have no direct effect over Carter.
The third and fourth quotes could have an effect on the unfolding of the plot only if the reader knew about the horseman's identity before the climax, the third one explaining how Carter would become an enemy to his father by joining the Union; the fourth one stating their possibility of becoming military casualties of war, rather than civil casualties.
