Although the 15th amendment was added to insure the voting rights of african american citizens this right was restricted by state

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." Although ratified on February 3, 1870, the promise of the 15th Amendment would not be fully realized for almost a century.

The correct answer is c