Lincoln's main objective in the Civil War was to have a superior military to the Confederacy in order to preserve the Union. While he wanted a superior military, he did not want to lose the border states by announcing that he was against slavery, as this would hamper his goal towards building a military.
The answer is C. he was pro-slavery, as he eventually released the Emancipation Proclamation in 1863 that freed all slaves in the South.
Because at any given time the soviets could set the missiles off and attack the US from all sides and we would have no way to stop it. It would also be attacking some of the most important places in the US