Which of the following BEST describes the reaction of Southern states to Lincoln's election? The Southern states agreed to form the Confederate States of America. The Southern states passed a pledge to leave the Union if they felt coerced to end slavery. States in the Deep South broke away so they could continue slavery but states in the Upper South supported ending it. States in the Deep South broke away immediately, but states in the Upper South chose to stay as long as slavery was in place.

Out of those options I'd say that 1 is the correct answer. The Southern states had been deeply suspicious of Lincoln prior to his election victory. They believed—wrongly, as it turned out—that he was determined to abolish slavery completely. Though Lincoln personally loathed the institution of slavery, his priority was to keep the Union together, even if it meant that every last slave remained in bondage. But the South was in no mood to pay attention to Lincoln's position. The national mood was feverish, with opinions on the issue of slavery deeply divided.
Just over a month after Lincoln's election victory, South Carolina became the first state to secede. They were followed in due course by the other ten states of the Confederacy, right up until Tennessee on 8th June, 1861. The Confederacy itself had already been established by that time at the Montgomery Convention in February 1861, a month before Lincoln's first inauguration.
https://www.history.com/topics/american-civil-war/secession