Answer: b) It allows the reader to see the contrast between the dogs sensible thoughts and the mans illogical thoughts.
Explanation: in "to build a fire" the narrator is omniscient to have the ability of telling us what the man is thinking but also what the dog is thinking, by using this contrast, the narrator judge the man by saying things like he has no imagination and that he is materialistic and doesn't care about the significance of things. Also the narrator emphasizes in how the dog is aware of the situations and how it experiences life.