A.The Rifle. The telegraph was invented after the Civil War, nobody really used observation balloons, the ironclad was a major invention but was not used too much, and the grenade was not used as much as the rifle.
The answer is a.rifle. Repeating rifles were most significant weapons during this war era. These rifles were convenient and very quick to load. This also served as the primary weaponry in battlefields and in the war zone. Rifles definitely provided a notable advantage to the militaries during the civil war.
