Answer: After reading the excerpt a few times, the most logical choice is "White Fang is unsure of how to act and only trusts his mother"
Step-by-step explanation:
White Fang, which I can only assume is the cub, is witnessing these strange men pet his mother and he doesn't seem to understand why. It couldn't be that he needs to protect his mother because it is established that he doesn't register their "noises" as anything that presents harm, although he is still somewhat weary. There's also no indication that this excerpt is a reunion scene, so we can also cross the "happy to see his mother" off the list, which leads to only recognizing the men and trusting his mother. White Fang has no idea who these men are, but since his mother is apparently okay with being petted, then he has to trust that she's right. And that's why it only makes sense to me that it's the correct answer.