Final answer:
The Selective Service Act required all men aged twenty-one through thirty to register for the draft. It was later expanded to include all men between eighteen and forty-five.
Step-by-step explanation:
The Selective Service Act required the following:
All men aged twenty-one through thirty to register for the draft.
All men between eighteen and forty-five to register for the draft.
The act was expanded in 1918 to include all men between eighteen and forty-five.
The purpose of the act was to create a fighting force during times of war.