Which sentence uses correct punctuation?
for my history paper, i chose three key american battles, lexington, gettysburg, and bull run.
voltaire wrote this about personal freedom, “i disagree with what you say and will defend to the death your right to say it.”
rachel finally decided on a major for college, physics.
we saw several national landmarks on our summer vacation: mount rushmore, the washington monument, and the grand canyon.

I know this is extremely late, but I got D -gradpoint

We saw several national landmarks on our summer vacation: Mount Rushmore, the Washington Monument, and the Grand Canyon.

A colon should be used before listed items when the sentence can actually stop at the colon. This sentence is a complete sentence before the list of landmarks. The colon allows the landmarks to be listed after, but still connect them to the sentence. Option 1 should have a colon after battles and Option 3 should have a colon after college for these same reasons.

gregor could have been bullying her