What is one responsibility of U.S. citizens?

One of the key responsibilities of U.S. citizens is paying taxes. This duty contributes to the functioning of government at local, state, and federal levels by providing necessary funds for public services and infrastructure. Taxes support a variety of essential services, including education, healthcare, transportation, and national defense. Through their payment of taxes, citizens participate in the economic framework that sustains public welfare and upholds democratic governance.

The other options, while related to governance and law enforcement, do not represent responsibilities of citizens. Issuing passports is primarily a function of the government, particularly the Department of State. Regulating commerce falls under the federal and state governments' responsibilities, handled by various regulatory agencies. Enforcing laws is a responsibility designated to law enforcement agencies and not a direct obligation of citizens.