"the gettysburg address" suggests that the civil war was a conflict that would tell, once and for all, whether

1. a number of competent union generals can overcome confederate general robert e. lee

2. the confederacy can win the war without the advantage of manufacturing centers

3. a nation founded on the principles of liberty and equality for all people could endure

4. the powers of state governments should supersede the powers of the federal government

3. a nation founded on the principles of liberty and equality for all people could endure

Explanation:

The Gettysburg Address was a speech by Abraham Lincoln in 1863, in the Civil War.

This following citation of the address is important to solve this question

"Fourscore 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."

So the correct answer is:

3. a nation founded on the principles of liberty and equality for all people could endure

be more specific with your question.