My parents (not huge animal lovers) answered "C" much to their surprise, when I was around ten years old. Our dog had a rare blood disorder (which we strongly suspect was brought on by our neighbor's poison attempts) which required regular and expensive treatments and surgeries. One night, Smokey had a horrible attack, and my father drove three hours at 2am in the morning to take him to the closest animal hospital open at the time. He drove him to that hospital on at least two other occasions, and paid a phenomenal amount of money (despite us not being particularly wealthy) to keep that dog with us. My parents always left the choice up to us kids as to what Smokey's fate would be, telling us that they would do whatever they could to support it. Ultimately, I made the decision and convinced my brothers that Smokey was in too much pain and that we had to let go, for his sake. We gathered around and took turns petting him, crying and laughing about all the great times we'd had with him.

I think my parents had a remarkable insight into that whole situation. They really allowed us to work through it on our own terms and were truly responsible pet owners (and great parents). If that were to happen again, with me as the adult, I would do everything I could, and not thinking about the money as much as the effectiveness of the treatment, quality of life, etc.