Which of these was NOT a cause of the Civil War?

A - The execution of John Brown led northerners to view him as a martyr while southerners began to militarize for future raids.

B - Popular sovereignty resulted in violent fighting over the status of new states being free or not.

C - President Lincoln ordered the attack on Fort Sumter off the coast of Charleston, South Carolina.

D - The North wanted to abolish slavery, while the South depended on it for its economy.​