※ 밑줄 친 부분에 들어갈 가장 적절한 것을 고르시오. [문 17～문 20] Why do we reach for a candy bar at the end of a heavy meal? We certainly are not hungry. Why do we like salt and other seasoning in our food? Soldiers who have been temporarily deprived of salt report that at its maximum intensity the craving for salt is more insistent than the desire for food itself. Cows and other livestock which are not receiving enough lime eat the bones of other animals to relieve the craving. These conditions are not thoroughly understood at present but it seems certain that somewhere in the body there are receptors which respond to the chemical conditions in the blood brought about by the absence of certain substances necessary for the body. When these receptors perceive such conditions, we have _______________________________