After the Election of 1860, states in the southern portion of the country withdrew from the United States. Lincoln attempted to preserve the Union by invading the South, starting what became known as the Civil War.
As for B he hated sectionalism he wanted to keep the united states, United For C, the Emancipation Proclamation was not his primary goal only a stepping stone For D, this was not his MAIN goal he first had to worry about keeping the states united and the union preserved before he could think about ending slavery