Answer:
D. The direct election of US senators.
Explanation:
In response to the widespread of corrupt practices of United States election of Senators in some states, the Seventeenth Amendment was passed to stopped the inefficiency and heavily exploited Article I, Section 3, Paragraph 1, of the Constitution, which stated that two of the United States Senators from each State should be chosen by the Legislature thereof.
However, in the bid to curb the loopholes and corrupt practices relating to the election, Seventeenth Amendment of the United States Constitution, made in 1913, stated that two Senators from each State should be elected by the people thereof, and state executive to fill vacancies in the Senate by making temporary appointments to serve before the new elections.
Hence, the political reform that was introduced by the 17th amendment is: the direct election of US senators.
