It really depends on which kind of 'leadership' you are looking for, however, your answer should be B. Lincoln.
While he did not lead armies to victory, he set the groundwork for a successful motive in winning the war. He was also able to gather most of the North together to fight the South, as well as build a " Team of Rivals"® (Doris Keams Goodwin), and use the team to be able to obtain the goal that he wanted. Even though it was a odd mix, with the differences of beliefs between the group, they were able to find ways to not only win the war, but to deal with the 'future'. Sadly, he was assassinated by John Wilkes Booth, and was not able to see much of the fruits of the war.
hope this helps
