What did the South gain from the Compromise of 1850? Slavery would be legal in Washington, DC.
Congress would pass the Fugitive Slave Act.
California would enter the union as a slave state.
Popular sovereignty would decide the slavery issue in Missouri.

Congress would pass the Fugitive Slave Act.

Explanation:

Compromise of 1850 include the Fugitive Slave Act that was passed by congress and the act was between southern slaves interest  and northern free slaves.

According to this act, all the free slaves or other slaves were asked to return to their owners.

Other actions under Compromise of 1850 are  abolishment of slave trade in Washington, D.C and California became the Union as a free state.

Hence, the correct answer is "Congress would pass the Fugitive Slave Act."

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