阅读选择：阅读下面短文，请从短文后所给各题的四个选项(A、B、C、D)中选出一个最佳选项。

     Prince was an intelligent dog and a slave to Williams. From morning till night, when Williams was at home, Prince never left his sight. The dog had a number of clearly defined duties, for which Williams had patiently trained him and, like the good pupil he was, Prince lived for the chance to demonstrate his abilities. When Williams wanted to put on his boots he would murmur "boots" and within seconds the dog would drop them at his feet. At nine every morning Prince ran off to the general store in the village, returning shortly not only with Williams' daily paper but also with a half-ounce packet of Williams' favorite tobacco. A gun-dog by breed, Prince possessed a large soft mouth specially evolved for the safe carrying of hunted creatures, so the paper and the tobacco came to no harm, never even showing tooth mark.
     Williams was a railway man, and he wore a blue uniform that smelled of oil fuel. He had to work at odd times, "days,""late days"or "nights." Over the years Prince got to know these periods of work and rest, and knew when his master would leave the house and return. If Williams overslept, Prince barked at the bedroom door until he woke, much to the annoyance of the family.
     A curious thing happened to Williams during the snow and ice of last winter. One evening he slipped and fell on the icy pavement somewhere between the village and his home. He was so badly shaken that he stayed in bed for three days; and not until he got up and dressed again did he discover that he had lost his wallet. The house was turned upside down in the search, but the wallet was not found. Two days later, Prince dropped the wallet into Williams' hand. Very muddy, stained and wet through, the little case still contained fifty-three pounds, his driving license and a few other papers. No one could tell where the dog had found it. Perhaps he had found it by the faint oily smell on the worn leather.