We elect a U.S. Senator for how many years?

Why this is the answer

A senator is elected for six years. The Framers wanted senators to be independent of passing public opinion, and a fairly long term was how they arranged it. It also balances the House, whose members serve two years and therefore follow public opinion much more closely. Senate elections are staggered so the chamber is never replaced all at once: they fall on even-numbered years and about a third of the seats come up every two years. The Constitution sets no limit on how many terms a senator may serve. Memory hook: six for the Senate, two for the House, and only a third of the Senate at a time.