What is one responsibility that is only for US citizens?

Serving on a jury is a responsibility that is uniquely designated for U.S. citizens. In the American legal system, being part of a jury is a vital function that allows citizens to participate directly in the judicial process. This responsibility ensures that a diverse group of individuals, representing various backgrounds and perspectives, is involved in making decisions on legal matters, which is essential for upholding the principles of justice and fairness in a democratic society.

Only citizens, as opposed to legal residents or non-citizens, are eligible for jury duty because juries are fundamentally composed of individuals who have a vested interest in the laws and governance of the country they reside in. This requirement reinforces the concept that jury service is a civic duty tied to citizenship, reflecting the social contract between citizens and their government. In contrast, the other options listed, although also associated with civic responsibilities, do not require citizenship specifically. For instance, paying taxes and obeying laws are obligations that apply to everyone residing in the U.S., including non-citizens. Working for the government can involve both citizens and non-citizens, depending on the positions. Thus, the unique link between jury service and citizenship makes it the correct answer.