What happened to the population of rural areas of city areas

Why did the north agree to the missouri compromise? a.) it allowed maine to enter the union as a free state. b.) it repealed the fugitive slave law. c.) it allowed california to enter the union as a free state. d.) it banned slavery in the northwest territory.

Ineed on 2-4 i want y’all to reply to this question so i can turn this into my teacher tomorrow

What is the name for the main idea behind the settling of western lands by americans in the early-1800s?