There was once a professor of medicine, who was very strict with the students.Whenever he took the chair on the exam committee , the students would be in fear, because he was hardly pleased with the answers they gave.A student would be lucky enough if he or she could receive a good mark from him.At the end of the term, the students of medicine would take their exam again. Now a student entered the exam room and got seated before the committee.This student was a little nervous as he knew it would not be so easy to get through the exam at all. The professor began to ask.The student was asked to describe a certain illness, his description of which turned out to be OK.Then the professor asked about the cure for the illness , and the student , too , answered just as right. "Good," said the professor, "and how much will you give the patient?"  "A full spoon," answered the student.  "Now you may go out and wait for what you can get," said the professor. At the same time the committee discussed carefully the answers the student had given.Suddenly the student noticed that there was something wrong with his last answer."A full spoon is too much," he thought to himself.Anxiously he opened the door of the room and cried, "Mr. Professor, I've made a mistake! A full spoon is too much for the patient.He can take only five drops."  "I'm sorry, sir," said the professor coldly, "but it's too late.Your patient has died." The students were afraid of the professor because   _   .
he often misunderstood them and gave them bad marks they often angered and disappointed him their answers often astonished him their answers hardly pleased him