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

Villages in developing countries often lack many things--books, clean water, electricity. These shortages are easy to see. But a different kind of shortage is not easy to see. That is a 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 expert system. There’s a way to ease these problems. They can do it with computers. In the past few years, computer scientists around the world have developed what they call expert systems. An expert system is a special kind of computer program. In some situations, it can take the place of a human expert. For example, an expert in medical system can help care for a sick person. A question appears on the computer screen, "Is the 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 normally?" 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 a 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 businesses.