Read this excerpt from The Call of the Wild by Jack London. By afternoon, Perrault, who was in a hurry to be on the trail with his despatches, returned with two more dogs. "Billee" and "Joe" he called them, two brothers, and true huskies both. Sons of the one mother though they were, they were as different as day and night. Billee's one fault was his excessive good nature, while Joe was the very opposite, sour and introspective, with a perpetual snarl and a malignant eye.

Why does the author include this detail?

It is a part of the exposition that describes Buck’s teammates.
It is a part of the exposition that shares Perrault’s family tree.
It is a part of the rising action that describes a brutal dog fight.
It is a part of the rising action that shows Buck making friends.