Why did the dred scott decision alarm northerners?

a. the dred scott decision gave a missouri slave the right to sue for freedom because he had moved to a free state.

b. the dred scott decision allowed african americans living in the north to be sold as property to plantation owners.

c. the dred scott decision ruled that, while staves were property, their descendents could sue in court for their freedom.

d. the dred scott decision declared the missouri compromise unconstitutional and ruled that slaves were property.