The correct answer is C.
Dred Scott v. Sandford was a landmark decision enacted by the US Supreme Court in 1857. Dred Scott was a black man and also a slave, who sued for his freedom when he was taken by his owners to free states.
The final decision stated that a black person, either free or slave, if he or his ancestors had been sold in the US as slaves, could never become an American citizen. Therefore Dred Scott could not have the right to sue in a federal court, as he could not be considered a citizen. It also was also decided that the federal goverment would not have power to rule slavery in territories acquired after the creation of the United States, therefore this meant a victory for the Southern pro-slavery states.