Answer:
A. The Senate
Explanation:
The Senate is composed of 100 Senators, 2 for each state. Until the ratification of the 17th Amendment in 1913, Senators were chosen by state legislatures, not by popular vote. Since then, they have been elected to six-year terms by the people of each state. Senators’ terms are staggered so that about one-third of the Senate is up for reelection every two years. Senators must be 30 years of age, U.S. citizens for at least nine years, and residents of the state they represent.
https://www.whitehouse.gov/about-the-white-house/our-government/the-legislative-branch/