It is important for all men age 18 through 25 to register for the Selective Service. Name one reason why.

What does this answer mean?

USCIS accepts three reasons why men 18 through 25 should register for the Selective Service: it's required by law, it's a civic duty, or it makes the draft fair, if needed.

The Selective Service System keeps a list of men who could be called to serve in the military if Congress and the president ever bring back a draft. Registering puts a man on that list.

The Selective Service says virtually all men in the United States between 18 and 25 must register, including U.S.-born and naturalized citizens and most immigrants, such as permanent residents. A few groups, such as men here on certain temporary visas, are exempt.

The "fair" answer refers to how a draft would work: a complete list means that, if a draft were ever needed, men could be selected from everyone who is eligible.

Selective Service registration also comes up in the Form N-400 instructions, and our guide to the documents for a citizenship application explains what those instructions ask for.

At the interview, the shortest answer is "required by law."