题目内容：
The dog, called Prince, was an intelligent animal and a slave to Williams. From morning till night, when Williams was at home, Prince never left his sight, practically ignoring all other members of the family. 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 with a half-ounce packet of Williams’ favorite tobacco, John Rhiney’s Mixed. 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 a tooth mark.
Williams was a railwayman, an engine driver, and he wore a blue uniform which smelled of oil and 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, knew when his master would leave the house and return, and the dog did not waste this knowledge. If Williams overslept, as he often did, Prince barked at the bedroom door until he woke, much to the annoyance of the family. On his return,
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