How does thoreau describe his reason for moving to the woods in lines 26-40? how do these lines relate to his purpose in writing walden

i would say the correct answer is not concrete.

b is the answer.   i sat on the lumpy sofa, totally exhausted, with a bad taste in my mouth, wondering what i should do next.  

the answer is b. the tracer looks harmless in flight, but the pilot’s bitten lips and white knuckles suggest how dangerous it can be.