Why do rabbits from polar regions have white fur?

Fa o compunere despre o casa in copac va rog frumos i-au nota

But we pulled at the grill [on the ground] and it gave way. and then we saw iron rings as steps leading down a shaft into a darkness without bottom. … it was a great tunnel. its walls were hard and smooth to the touch; it felt like stone, but it was not stone. on the ground there were long thin tracks of iron, but it was not iron; it felt smooth and cold as glass. we knelt, and we crawled forward, our hand groping along the iron line to see where it would lead. but there was an unbroken night ahead. what is the most likely explanation for the walls described in the bold text?

What is most likely steinbeck's overall reason for writing travels with charley? to give readers facts about the western landscape to observe life in the largest cities in america to show life in different parts of america to support his argument that new york city is better than rural america