What is the purpose of a passport?

A passport serves as an official document issued by a government that certifies a person's identity and citizenship, primarily for the purpose of international travel. It allows a person to travel abroad and re-enter their home country, as it identifies them as a national of that country.

The correct answer highlights this fundamental role of a passport, as it confirms an individual's U.S. citizenship, which is crucial for embassies and customs authorities when citizens are traveling in foreign countries. Additionally, it provides vital information such as the holder’s name, photo, and nationality, which can be used to authenticate their identity during travel.

The other options do not accurately reflect the purpose of a passport. For example, a passport is not related to voting rights, government aid programs, or voter registration, as these functions are served by different documents, such as voter ID cards, Social Security cards, or proof of residency. This emphasizes the unique and specific role that a passport plays in international travel and citizenship identification.