Final answer:
In 'To Build a Fire', 'It was unbroken white' is compared to the extensive and uniform white snow covering the landscape, with a contrasting dark line representing the trail.
Step-by-step explanation:
In paragraph 1 of 'To Build a Fire', the author is comparing the phrase 'It was unbroken white' to the environment's vastness and the uniform whiteness of the snow-covered landscape. This comparison is made to the Yukon trail and the snow that lies atop the ice, highlighting the extreme conditions and the isolation of the setting. The contrasting dark hair-line represents the trail, which is a path through the white expanse, symbolizing the direction and hope in the desolate surroundings.