Buck’s fear of the unknown world in the wild is the correct answer.
Explanation:
The Call of the Wild is a short novel by American novelist Jack London, and its main character is Buck, a dog that is stolen from his house and then sold as a sledge dog. The novel narrates Buck's process of becoming feral little by little.
In the excerpt, the hairy man is described with words that remain the unknown world in the wild, since the narrator uses words like "hairy man" (the amount of hair could represent something that is not easy to control, like the wild itself) who is sleeping by "the fire", meaning that they are surrounded by the darkness. Also, the man's behavior seems to remind of wild things because of the way he slept (restlessly, like if he were aware of the danger that comes with the wild.)
