What did the Supreme Court rule in the Dred Scott decision?

The correct answer is: **a. that the Missouri Compromise was invalid.**

In the Dred Scott v. Sandford decision of 1857, the Supreme Court ruled that the Missouri Compromise, which restricted slavery in certain territories, was unconstitutional, and that African Americans could not be considered citizens. The Court did not declare slavery unconstitutional nor did it rule that Dred Scott was a free man.