Thoreau lived on Emerson's land, which was the subject of one of his books.
The correct answer for this would be option B. Based on the given sentence above, the highlighted part of the sentence which is "<span>who had been to the mansion before," is called an appositive phrase. This is considered as an appositive phrase because it renames or describes the noun next to it. Hope this helps.</span>
Answer:
an argument or main idea
Explanation:
backs up the evidence that supports the idea or thesis statement or main idea
