Which of the following is an example of a claim that a historian might make about the American Civil War? A. The Emancipation Proclamation freed slaves only in states that had seceded from the Union. B. The American Civil War had many causes, and this paper will explain them all. C. Former slaves fighting in the Union army were essential to several Northern victories. D. President Lincoln wrote in a letter, "If I could save the Union without freeing any slave I would do it."