A.Lack of clean water. B.Lack of electricity. C.Shortage of books. D.Shortage of experts. 17. A) A system which trains doctors. B) A group of experts who can provide professional advice. C) A computer program which can provide professional advice. D) A system which trains computer experts. 18. A) It is not easy to see the shortage of experts in the villages. B) Many doctors and engineers are sent to the villages to make up for the shortage of experts. C) Expert medical systems are widely used in developing countries. D) Expert systems are owned by wealthy farmers and businessmen.