Answer:
A. Because being imprisoned only affects the body, not the mind
Step-by-step explanation:
Imprisonment is being done to the people who are not conforming to the societal standard, so they are locked away with the hope that they do not hurt or 'ideologically contaminate' other people.
Thoreau argued that such imprisonment wouldn't fix the difference in way of thinking that cause that people to be imprisoned to begin with.
During the period of the imprisonment, the prisoners will still constantly re-examine their ideologies that put them there in the first place. Their belief might get deepen since they only have other prisoners to interact to, which are also considered 'misfits' of society.