Answer:
The correct answer is His insticts.
Step-by-step explanation:
White Fang is the protagonist of this story, an animal seen at the beginning of the book as a mischievous and impetuous creature. He is the youngest of five siblings and the only survivor, thanks to his mother he manages to move to a town, where he has his first contact with the man.
As the passage shows, the fact that White Fang knew where to attack the dog was a legacy knowledge of his hunting ancestors, that is, it was already part of his instinct as a hunting wolf.