Which group of adult males,ages 21 to 30,was not required to serve in the u.s. military during world war 1

Conscientious objectors. The United States government wanted as many men as they could get to join the force voluntarily. However, a law was passed in 1916 establishing that men had to register regardless of their will. Conscientious objectors were those men who were refusing to join the forces for moral or religious reasons. There were about 16,000 of them who were either sent to prison or allowed to do non-military work (like farming or as strecher-bearers on the battlefields) since their conscience didn't allow them to kill.

B. Federal

Explanation:

The current form of government in the United States today is the Federal form of government. This is because it divides power between the central national government and the state governments in the country.

Thereby consisting of checks and balances which limits the power of the central national government by balancing it with the power of the States