Which of the following was a constitutional provision that forbade any state from denying suffrage on the basis of race, color, or previous condition of servitude?

If memory serves me correctly it was the 15th amendment.

The 15th Amendment to the Constitution of the United States was the constitutional provision that forbade any state from denying suffrage rights on the basis of race, color, or previous condition of servitude. The Amendment was passed by Congress on February 26th of 1869, and was ratified on February 3rd of 1870. Although the 15th Amendment, in the context of the end of the Civil War and the end of slavery in America, was a historic landmark for civil rights in the country, it was not completely applied for over a century. It was the ratification of the Voting Rights Act in 1965 that officially ended the discrimination against people of color when it came to their voting rights.