Which responsibility is NOT required of a citizen of the United States?

Serving in a legislative position is not a legal requirement for U.S. citizens. While holding public office, including legislative roles, is a civic duty that some citizens choose to undertake, it is not mandated by law. The Constitution and federal laws establish certain duties for citizens, such as the obligation to serve on a jury when summoned and to serve the country in times of need, which highlights active participation in civic life. Additionally, fostering tolerance towards others strengthens community cohesion and is an important societal expectation, but it doesn't carry legal weight as a duty. Thus, among the options presented, only serving in a legislative position is not an obligatory responsibility for citizens.