What is one responsibility of U.S. citizens?

One of the key responsibilities of U.S. citizens is to pay taxes. This obligation helps fund essential services and infrastructure that benefit society as a whole, such as public education, transportation, and defense. Taxes are a fundamental aspect of civic duty, as they contribute to the functioning of government and the provision of services that support the well-being of all citizens.

The other options, while valuable, do not constitute core responsibilities of citizenship. Speaking multiple languages can be beneficial but is not a requirement; community service is commendable but voluntary; and traveling abroad, while often encouraged, is not a responsibility of citizenship. Paying taxes stands out as a clear and necessary duty.