An effect of the Supreme Court’s ruling in Scott v. Sandford was that

In Scott v. Sandford (the Dred Scott decision), the Supreme Court ruled that Congress could not prohibit slavery in U.S. territories. It also denied that people of African descent could be U.S. citizens. These rulings strengthened legal protection for slavery, making A the correct choice; the Court actually struck down the Missouri Compromise rather than strengthening it.

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