Which amendment allows for the direct election of Senators?

The Seventeenth Amendment is the correct answer as it specifically provides for the direct election of Senators. Ratified in 1913, this amendment altered the original process established by the Constitution, which allowed state legislatures to choose their Senators. The change was motivated by concerns about corruption and the lack of accountability in the legislative appointment process. The Seventeenth Amendment ensures that Senators are elected directly by the voters of each state, thus enhancing democratic participation and ensuring that Senators are more responsive to the needs and desires of their constituents.

In contrast, the Sixteenth Amendment deals with the federal income tax, the Nineteenth Amendment guarantees women the right to vote, and the Twenty-Third Amendment grants residents of Washington, D.C. the right to vote in presidential elections. Each of these amendments addresses different aspects of the electoral process or government authority, but none pertain to the direct election of Senators.