Read the passage from Part 1 of “To Build a Fire.” It was a clear day, and yet there seemed an intangible pall over the face of things, a subtle gloom that made the day dark, and that was due to the absence of sun. This fact did not worry the man.

How does this detail about the setting advance the plot?

It introduces the difficulty the man will face with the darkness.
It explains the cold temperatures that are reached without the warmth of the sun.
It suggests that the man is unable to observe his surroundings.
It shows the man’s lack of concern despite his situation.