Which statement correctly explains the reasons that the compromise of 1820 and the compromise of 1850 were unsuccessful at solving the nation's issues?

slave labor was such an important part of the american economy that most northern states stopped opposing slavery.
slave and abolitionist rebellions in virginia and kansas convinced most americans that slavery was not worth fighting for.
escaped slaves became voting citizens in the north and did not want their representatives to compromise with the south.
congress could not control the states' desire to make their own laws, and dependence on slavery grew in the south while opposition to it grew in the north.