题目

What is so amazing about giving blood?    The National Blood Service, which covers all of England and North Wales, needs nearly two and a half million blood donations each year. When you give blood, you’ll be doing one of the most amazing things anybody could dream of — saving a life. ___________________________ All types of blood are needed —not just rare ones. In fact, the commoner the blood type, the more are needed. So even if your blood is one of the most common types — group O for example — you can be sure that by donating three times a year, you really are doing so在图中过点A分别画出钝角两条边的平行线和垂线．