阅读理解。 Every year, World Blood Day is celebrated by blood services worldwide on 14 June, the birthday of Nobel Prize winner Karl Landsteiner, the man who discovered the ABO blood group system. If you have every thought of becoming a blood donor, just register to do it. And you should never worry about the donation. Just under a pint (around 470ml) of blood is taken at one sitting. This amount is no more than 13 percent of your total blood volume, and is quickly replaced by your body. It may come as a surprise, but whole blood is only rarely used. Different blood components are used to treat a range of conditions. None goes to waste. Red blood cells are frequently used to replace heavy blood loss after an accident, surgery or childbirth. White blood cells and antibodies (抗体) are used to help people fight infections if their immune system doesn't appear to be responding to antibiotics (抗生 素). Plasma (血浆), the straw-coloured fluid which carries the blood cells and contains proteins, are used to treat burned patients. First-time donors should be aged between 17 and 65, weigh at least 50kg and be in good health. If you have donated before, you can start being a donor again up to your 70th birthday. Although most people are able to give blood, some people who pose health risks or are at a higher risk of having come into contact with an infectious disease are no tasked to be donors. Pregnant wo men or those who have h ad a baby in the last 9 months should not donate blood. Blood has a very short shelf life. Some blood components can be kept longer than others, for instance red blood cells will keep for 35 days but platelets(血小板)for only five. Remember, you should wait at least 16 weeks before donating blood again. 1. People should never worry about the donation mainly because _____. A. it causes no pain to their body B. being a blood donor is a great honor C. their bodies can produce new blood soon D. people have a mature research on it 2. What component of blood is used to treat burned patients? A. Plasma B. Red blood cell C. Antibody D. White blood cell 3. We can learn from the passage that _____. A. whole blood is most widely used in hospital B. platelets can be kept for more than 10 days C. people can donate their blood four times a years D. people can donate at most 470 ml of blood each time 4. Who can donate their blood? A. A teenager who is studying in a primary school B. A mother who is about to give birth to a new baby C. An adult who smokes and drinks from time to time D. A man just coming back for a place suffering from malaria 5. What is the purpose of the author in writing this passage? A. To teach people how to be a blood donor B. To give people the knowledge of blood donation C. To advise people to benefit from blood donation D. To remind people of the importance of blood donation