[单项选择]Of the thousands of different kinds of animals that exist in the world man has learned to make friends with an enormous number. Some are pets, and offer him companionship; some give protection, and some do hard work which man cannot do for himself. Dogs, which serve man in all three capacities, are found in various breeds in all countries of the world. The Husky can live in the cold polar regions, and the Saluki is at home in the hottest parts of Central Africa. The inhabitants of certain countries are dependent for their very lives on the camel. In the West Indies the little donkey, strong and sure-footed, carrying heavy loads even in mountainous places, is a familiar sight.
Trained and tamed for many generations, domestic animals are not accustomed to roaming(到处走动) in search of food and shelter. They look to their masters to provide for their needs, and as long as these are supplied, they are contented to do what their masters require.
All domestic animals need proper food.
A. There exists thousands of species of animals in the world.
B. Man came to establish a close relationship with a number of animals.
C. In some regions a donkey seems to be a very useful beast.
D. An animal will be useless unless domesticated.