Final answer:
The Senate is called a "continuous body" because only one-third of the Senate is up for reelection at any given time, ensuring continuity and stability.
Step-by-step explanation:
The Senate is called a "continuous body" because it operates under a system of staggered terms, where only one-third of the Senate is up for reelection at any given time. This means that senators serve for six-year terms and elections are held every two years, but not all seats are up for election simultaneously. This system ensures that the Senate maintains continuity and stability, allowing experienced senators to provide institutional knowledge and expertise.