The selma-to-montgomery civil rights march and the violent response it attracted led to:

The Selma to Montgomery  march, and the participation of Martin Luther King, Jr.’s in the historic march raised awareness of the difficulties faced by black voters, and the need for a national Voting Rights Act. Consequently, it led Congress to pass the Voting Rights Act in August of 1965. This guaranteed the right to vote to all African Americans.

a, a, a

(Selma, three attempts, the Voting rights act)

Explanation:

d. promised it other land

confederacy: supported slavery, believed states should be able to nullify federal laws, supported low tariffs

union: everything else