Which sentence from "The Gettysburg Address" most effectively states the central claim of this passage?

"It is for us the living, rather, to be dedicated here to the unfinished work which they who fought here have thus far so nobly advanced."

"Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal."

"Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure."

"The world will little note, nor long remember what we say here, but it can never forget what they did here."