I'm pretty sure the answer is government agencies
The answer is C. <span>The necessary and proper clause
</span><span>The necessary and proper clause means that all the law/regulations created by the government shall be necessary and proper according to the situation that is faced by the nation. For example, the nation could make a law that require all males to join military in when the nation face a crisis in a war.</span>
So, the power seems to be with the citizens - they are the ones who make the decision whom to elect.
So the general system is democracy - the power is with the people.
However, the people don't make their decisions directly, but they choose some others to represent them - this is called representative democracy.
There are a lot different answers to this question so what specific things are you looking for?