Why was the 15th amendment added to the bill of rights?

The 15th Amendment to the Constitution granted African American men the right to vote by declaring that the "right of citizens of the United States to vote shall not be denied or abridged by the United States or by any state on account of race, color, or previous condition of servitude."

may i see the answer choices?

the viking voyages took place during the middle ages, which was about this time. 500 to 1350. the viking voyages took place during the middle ages, which was about this time.