A、Lack of clean water. B、Lack of electricity. C、Shortage of experts. D、Shortage of books. C

Villages in developing countries often lack many things: books, clean water and electricity. These shortages are easy to see, but a different kind of shortage is not easy to see. That is the shortage of experts.
    Many villages have no doctors, engineers, or scientists. They have no one who knows how to treat unusual medical problems or design a new energy system. There is a way to solve these problems. They can do it with computers. In the past few years, computer scientists around the world have developed what they call expert system.
    An expert system is a special kind of computer program. In some situations, it can take the place of human expert. For example, an expert medical system can help care for a sick person. A question appears on the computer screen "Is this person hot?" You tell the computer either "Yes" or "No". The computer asks other questions, "Has the person lost any blood?" "Can the person move normal[y?" you answer. The computer continues to ask questions until it has enough information to make a decision. Then it tells what medicine or other treatment is needed. In this way, the expert system takes the place of a doctor. Another kind of expert system takes the place of an engineer. It measures the flow of water in the river. It tells if a dam can be built on the river. It also tells how much electricity can be produced. Still other kinds of expert systems help solve problems for farmers and owners of small business.