The correct answer is A) to win and end the civil war.
Indeed, the Gettysburg Address was given four and a half months after the Union victory at the battle of Gettysburg, in 1863. Before that battle, the Confederacy was winning the war and Lincoln was aware that even after this victory, the South remained a dangerous foe.
Therefore, although he was saluting the sacrifice of the dead Union Soldiers at Gettysburg, he wanted to make sure their sacrifices would not be in vain. Only total victory over the Confederacy would finish the work.
