A、It was full of energy. B、It gave out heat. C、It could cure illness. D、It could keep them healthy. C短文提到，古人认为牛奶有很好的治疗功效，healing

Milk was a basic food of man long before history was written. It will probably keep on being one as long as there are animals that give milk.
    Many ancient people thought that milk had great healing power. One of the most famous Greek doctors told his patients to drink milk to cure illness.
    For more than two hundred years most people got their milk from their own cattle or from a nearby dairy herd. But in time new inventions made the dairy industry a big business. In 1851 Gail Borden, founder of a milk company, found a way to take some of the water out of milk. This made it keep much longer. Four years later, Louis Pasteur introduced the pasteurization process. This process killed the bacteria in milk that caused it to spoil. Next, a special milk bottle was designed. This was followed by the invention of machines that could fill bottles and cap them automatically.
    These discoveries had a great effect on the dairy industry. They meant that milk could be stored longer. It could be safely shipped over long distances. Preparing and distributing milk soon became a large-scale business. Recently, in a single year more than sixty billion quarts of milk were sold in the United States.
    Some people believe that milk drinking will become less popular in America than it has been. But remember how long milk has been a basic food and think of the many ways in which it is useful. It seems safe to say that the milk industry will always be important.
12. What did ancient people think about milk?
13. Why did milk become a big business?
14. What invention made milk keep longer in 1851?
15. What does the speaker think of the milk industry in the future?