Onomatopoeia is a figure of speech which imitates sounds heard in nature. Having that in mind, the example of that figure in this poem would be moaning and groaning. The moaning and the groaning of the bells is a reference to the moaning and the groaning that animals and humans can produce.
Stay to your self and try to figure out things mentally
The correct answer is A: the consent of the people.
Jefferson makes it very clear that the source of a government's authority is the consent of the people. He uses the phrase "consent of the governed," which means the people (since they are the ones who are governed).
He does not believe a government's authority comes from tradition, the military, or a leader.