Thoreau mostly uses imagery to illustrate time in the excerpt. The second sentence is saying that he is in the midst of time/living, and he can "detect how shallow it is," meaning that he is aware that life is short and that the end is inevitable. Thoreau also describes time as being fleeting, but ever-present.
I hope this helps!
The right answer for the question that is being asked and shown above is that: "c. The novels and short stories written by explorers were too difficult to preserve and have been lost." the literature of exploration filled with so many journals, letters, and other nonfiction sources because <span>c. The novels and short stories written by explorers were too difficult to preserve and have been lost.</span>
