C has a misplaced adjective clause. It's supposed to be "I took my dog who began to bark to the veterinarian." C makes it sound like the vet started barking.
If sounds as if it refers to his aching agony within his situation. ¨Bear up, old heart! You´ve borne worse, far worse,¨ shows how everything is affecting him. This is his attempt to tell himself to stay strong in time of dispair.
