What does Fitzgerald's last line of the novel mean?

In The Great Gatsby, the last sentence reads: So we beat on, boats against the current, borne back ceaselessly into the past. This refers to the dualities of Gatsby and America.  Gatsby looked like a Romantic hero to Nick: he was a self-made man, a rags to riches story, a symbol of the American dream.

Explanation:

i think the answer is c.  

the price of our current war is high; it costs money and it costs lives.

but it does not cost our pride. it does not cost the guilt that would arise from knowing that we did nothing to intervene while our neighboring nations fell to despotic leaders.

it does not cost the terror of knowing that our allies are unstable. it does not cost the fear that we, too, will be next to fall.

which sentence most accurately explains why the speaker's use of the parallel structure is effective in this passage?

a. it underscores that disagreement will not be tolerated and will be dealt with swiftly.

b. it makes the speaker seem like a decisive and capable leader.

c. it emphasizes reasons to fight and inspires listeners to aid the war effort.

d. it establishes the speaker's credibility by acknowledging the difficulties of war.