Read this excerpt from The Call of the Wild by Jack London. And always they pitched camp after dark, eating their bit of fish, and crawling to sleep into the snow. Buck was ravenous. The pound and a half of sun-dried salmon, which was his ration for each day, seemed to go nowhere. He never had enough, and suffered from perpetual hunger pangs. Yet the other dogs, because they weighed less and were born to the life, received a pound only of the fish and managed to keep in good condition.

Why does the author include this detail?

It is a part of the exposition that introduces the dogs’ histories.
It is a part of the exposition that describes packing provisions for the trail.
It is a part of the rising action that shows Buck’s interaction with the other dogs.
It is a part of the rising action that explains a challenge Buck faces on the journey.