B. Both armies realized the war would be prolonged and costly.
Explanation:
The First Battle of Bull Run cost some 3,000 Union casualties, compared with 1,750 for the Confederates. For the Confederates, accusations flew between Generals Johnston, Beauregard and President Jefferson Davis over who was to blame for the failure. For the Union, Lincoln removed McDowell from command and replaced him with George B. McClellan, who would retrain and reorganize Union troops defending Washington into a disciplined fighting force, thereafter known as the Army of the Potomac.
I think that what Mandela means when he speaks of nation building is creating a world where everyone is equal and has rights. I think this because we know that there was a huge racial injustice at the time and Mandela was fighting for black rights. He also used the word reconciliation which means making a view or belief compatible with another or the restoration of friendly relations.