This sentence technically doesn't contain an error in verb-noun agreement, however the noun "each one" is odd here. It should be "everyone"
More than 90% of people in the coverage gap residing in the South
A. Whether the federal government should have the power to regulate slavery
I'm not really sure if you need a broad or detailed definition of the policy, but I'm assuming you want a broad explanation.
The US Policy of Containment was a policy put forth during the Cold War to limit the influence of communism around the globe by attempting to prevent the spread of communism from Russia to other countries around the world. Hope that helps :)
