Research about the civil war - where should I travel?

I'd go with D, only because you 1) you get to visit the state that had the largest number of Civil War battles (Virginia), 2) the state that was home to the capital of the Confederacy (also Virginia), 3) you get to take a look at a union state (Pennsylvania), a border state (Maryland), and a Confederate state (Virginia), so you can get a variety of perspectives on the Civil War, and 4) Pennsylvania is home to Gettysburg and that was just such an important battle in the war.