C. OAU. Organization of African Unity (OAU) had nothing to do with America.
Answer: the decision by the United States government to prevent additional settlement
Explanation:
What was meant by the "closing" of the Western frontier was that the United States government wanted to prevent additional settlement.
This decision was as a result of the government's plan to promote the westward expansion after the Civil War, but however, they had to close the Western frontier to prevent additional settlers.
Tavern culture was critical to the growth of revolutionary sentiment in the colonies, because taverns were where American patriots were able to group together and discuss how to start mini-revolutions which would lead up to the American Revolutionary War. The taverns also helped people living in rural areas learn how to do certain things, because there was a contact between people and this helped farmers learn new agricultural techniques (for example).
1st one is correct because I did the test