Final answer:
The text provided does not confirm that Bryan worked for over two hours on tearing the birchbark into slivers; instead, it focuses on the challenges of starting a fire in extreme cold conditions.
Step-by-step explanation:
The text excerpts provided do not explicitly mention Bryan working for over two hours tearing the birchbark into hair-like slivers. Instead, they describe a scenario in which a man's struggle to survive in extreme cold forces him to meticulously prepare a fire, referencing birch-bark as a material he uses to ignite a flame. The detailed processes that the man goes through to maintain body warmth, protect himself from the harsh weather, and gather materials to build the fire suggest a theme of survival and the importance of fire in extreme conditions.
Since the exact duration Bryan worked on the birchbark is not given, we cannot confirm whether he worked for over two hours on that particular task. Instead, the focus is on the painstaking effort required to initiate a flame under severe cold and the man's preparedness and persistence in the face of nature's challenges.