C, protection for the state citizens
Every government has three basic responsibilities: to protect, to provide and to invest.
The federal government has to protect its citizens from violence and ensure their rights as citizens are respected. The government provides the safety of law and order, protecting citizens from each other and from foreign enemies.
To protect its citizens, the government needs to collect taxes ( for the police and the army). The government deals with other governments in order to ensure there are no significant foreign threats.
elastic potential energy