The 13th, 14th, and 15th amendments.
General Dwight D. Eisenhower
After the civil war, much of the ownership for land was unattainable for free slaves due to the government opposing the idea. Instead most African slaves had to become sharecroppers on plantations where they had previously been slaves.
Congress passed the Civil Rights Act of 1964 using this Constitutional authority and this was a c) protection of state's citizens. The Civil Rights Act of 1964 is defined as a "landmark piece of civil rights legislation in the United States that outlawed discrimination based on race, color, religion, sex, or national origin."