He wrote it to inform I believe.
Answer:
Initially, Buck's response to the dognappers is one of quiet acceptance. But that's because he doesn't yet know he's being stolen. He instinctively trusts Manuel, and so has no reason to think that he's up to no good. So when Manuel places the rope around his neck, he accepts it with quiet dignity.
Explanation:
This is a hard one and I can see why you decided to post it here. B is most definitely wrong but the other three are all neck and neck. There are both even pros and cons of A and C but I think it would be more reasonable to adopt a general routine. So I think the answer would be C.