Long ago, operation usually had to be done while the sick man could feel everything. The sick man had to be held down on a table by force while the doctors did their best to save him. He could feel all the pain if his leg or arm was being cut off, and his fearful cries filled the room and the hearts of those who watched. Soon after 1770, Josept Priestley discovered a gas which is now called 'laughing gas'. Laughing gas became known in America. Young men and women went to parties to try it. Most of them spent their time laughing, but one man at a party, Horace Wells, noticed that people didn't seem to feel pain when they were using this gas. He decided to make an experiment on himself．He asked a friend to help him． Wells took some of the gas, and his friend pulled out one of Wells' teeth. Wells felt no pain at all. As he didn't know enough about laughing gas, he gave a man less gas than he should have. The man cried out with pain  when his tooth was being pulled out. Wells tried again, but this time he gave too much of the gas, and the man died. Wells never forgot this terrible event. 1. Long ago，when the sick man was operated on, he ______. A. could feel nothing B. could not want anything C. could feel all the pain D. could do anything 2. Using the laughing gas, the people did not seem to ______. A. be afraid of anything B. feel pain C. want to go to the parties D. be  ill 3. If a man took less laughing gas than he should have when an operation went on, he ______. A. felt nothing B. felt very comfortable C. still felt pain D. would die 4. One who took too much of the laughing gas ______. A. would laugh all the time B. would be very calm C. would never feel pain D. would die.