In the lines, “time is but the stream i go a-fishing in. i drink at it; but while i drink i see the sandy bottom and detect how shallow it is. its thin current slides away, but eternity remains, “ thoreau mostly uses imagery to

a. the beauty that is in the natural world.

b. the idea that he is unconcerned with dying.

c. his argument that everyone should move more slowly.

d. his belief that the passing of hours and days is irrelevant.