D. He uses metaphor to portray the government as something driven by greed and evil.
Explanation:
Option D is the correct answer.
Looking at the excerpt, we see that Thoreau actually uses metaphor. He likens the government as a machine. As all machines have their friction, there is need for some good in order to counterbalance the evil. The author sees that when the friction comes is likened to when oppression and robbery are set in and organized.
Metaphor is actually a figure speech that is used to compare two things. It is done without the use of "as" and "like".
