Candidates who want to run for the Senate must be at least 30 years old. Option C is correct.
Furthermore, a candidate who wants to run for Senate also must:
Be a U.S. citizen for at least 9 years prior to running
Live in the state that they are running for
Have these skills: Legal, business, or teaching experience; exceptional organizational, leadership, and also communication skills.
The qualifications to become a U.S. senator are stated in the U.S. constitiution; article one, section three and clause three.