Answer:
The sentence that best states the overall structure of Walden is The work describes Thoreau's thoughts over the course of a year spent immersed in the natural world.
Step-by-step explanation:
"Walden" by Henry David Thoreau talks about how he spent two years in Walden Pond, and goes through several topics seen by the new vision he got from being in contact with the nature and then going back to "civilization" as he mentions at the beginning of the book, he analyses social and economical topics from a different way of living.