What is the term of service for a US senator and how often are Senate elections held?

A United States senator serves a term of six years. This term length was established by the Constitution and is intended to provide stability and continuity in the Senate, which is one of the two legislative chambers in the United States Congress. The staggered elections occur every two years, meaning that approximately one-third of the Senate is up for re-election at any given election cycle. This staggered approach helps to ensure that there is not a complete turnover in the Senate, allowing experienced members to continue serving while newer senators can be elected.

The other options incorrectly describe the length of the term or the election cycle. Two years for a senator is not aligned with the constitutional standard, and elections held every three years would disrupt the staggered nature that is designed to maintain a balance within the Senate. Thus, the correct answer reflects the established practices of US Senate terms and election schedules.