The correct answer is D. One third of the seats in the Senate are up for election every two years.
Explanation:
The United States Senate is the upper house of the United States Congress, and together with the United States House of Representatives, the body from which federal legislation emanates. The composition and powers of the Senate are set forth in Article I of the Constitution of the United States. Each state is represented by two senators, regardless of their population, who are elected by uninominal majority scrutiny. The Senate chamber is renewed by thirds every two years. In this way a senator lasts 6 years in office, being able to be re-eligible.
