Final answer:
A U.S. senator serves a six-year term, while a U.S. representative serves a two-year term.
Step-by-step explanation:
A U.S. senator has a six-year term, while a U.S. representative has a two-year term.
This means that the correct answer to the student's question is that a senator serves for six years, and a representative serves for two years.
The Senate and the House of Representatives have different term lengths to balance the frequency of re-election with the ability to focus on public policy.