阅读理解 If you see someone drowning, speed is very important. Once you get him out of the water, if he isn't breathing, you have four minutes before his brain is completely destroyed.  Support his neck, tilt(使翘 起) his head back and press his chin (下巴) upwards.This stops the tongue blocking the airway in the throat and is sometimes enough to get him breathing again. If that doesn't work, start mouth-to-mouth breathing. Prees his nostrils (鼻孔) together with your fingers. Open your mouth and take a deep breath.  Blow into his lungs until his chest rises, then remove your mouth and watch his chest fall. Repeat twelve times a minute. Keep doing until help arrives. To bring a child back to life, keep your lips around his mouth and nose and gently blow into his mouth. Give the first four breaths as quickly as possible to fill the blood with oxygen. If, in spite of your efforts, he starts tuming a blue-grey colour, and you can feel no pulse (脉搏) , then pressing is the last chance of saving his life. With arms straight, rock forwards, pressing down on the lower half of the breastbone. Don't be too hard or you may break a rib(肋骨). Check how effective you are seeing if his colour improves or his pulse becomes independent to your chest pressing. If this happens, stopthe pressing. Otherwise continue until rescue amves. 1. This passage is mainly about . A. how to save people out of the water B. how to give first aid to people who are drowning C. how to do mouth-to-mouth breathing D. how to save a child from a nver 2. Once you get a drowning man out of the water, if he isn't breathing, you must first . A. get him breathing again B. take him to the nearest hospital as soon as possible C. find someone to help you D. call the First Aid Centre 3. In the last paragraph, the underlined word 'rescue' means . A. breath B. help C. doctor D. pulse 4. If the drowning boy has no pulse, . A. pressing his chin upwards is enough to get him breathing B. blowing air into his mouth is sure to save his life C. pressing his nostrils together with your fingers can work D. pressing is the last chance of saving his life