17．When you cut your skin，you bleed（流血）．If a person loses a lot of blood，he will become ill and may die．Blood is very important．People have always known that．At one time，some people even drank blood to make them strong!
When doctors understand how blood goes around inside the body，they try ways of giving blood to people who need it．They take blood from the healthy people and give it to people who need it．This is called"blood transfusion"．The blood goes from the arm of the healthy person into the arm of the sick person．
But there are two problems．First，it does not always work．Sometimes people die when they have blood transfusion．Later，doctors find that we do not all have the same kind of blood．There are four groups-O，A，B and AB．We all have blood of one of these groups．They also find that they can give any kind of blood to people of group AB．But they find that they must give A-group blood to A-group people and B-group blood to B-group people．I have O-group blood and the doctor told me that I could give blood to anyone else safely．
There is another problem．To give blood of the right kind，doctors have to find a person of the right blood group．Often they can not find a person in time．If they have a way to keep the blood until someone needs it，they can always have the right kind of blood．At first they find they can keep it in bottles for fifteen to twenty days．They do this by making it very cold．Then they find how to keep it longer．In the end they find a way of keeping blood for a very long time．
We call a place where we keep money a"bank"．We call a place where we keep blood a"blood bank"．One day，when you grow up，you may decide to give blood to a"blood bank"．In this way you may stop someone from dying．Or perhaps one day you may become ill．You may need blood．The"blood ban"will give it to you．
70．From the passage，we learn that sometimes people die when they have blood transfusions because they．C
A．are unhealthy people
B．have lost a lot of blood
C．are not given the right kind of blood
D．are AB-group people
71．Which of the following is true？B
A．Doctors can give any kind of blood to the writer．
B．The writer can give blood to B-group people．
C．The writer has never had a blood transfusion．
D．The writer has the same kind of blood as his father．
72．People set up the"blood bank"so that they can．A
A．give the right kind of blood to the people who need it in time
B．keep different groups of blood as much as possible
C．make it easier to sell or buy blood
D．keep blood for more than twenty hundred years
73．The writer doesn't talk aboutCin the passage．
A．how important blood is to us
B．the four groups of blood
C．where the blood bank is
D．what"blood transfusion"is．
分析 试题分析：这篇短文主要讲述血在我们的生命中是最重要的东西，人失血太多有可能会失去生命．在这种情况下，就会到医院输血．但是输血时还要先匹配血型，如果血型不符，被输血人还是会有死亡的风险．为了让失血过多的人可以在短时间内获得足够的血液，建立了血库，用于保存大量的血液供病人使用．献血既可以救人又可以在自己需要时使用，所以献血对自己是有好处的．
解答 70．C，推理判断题，文中提到"Sometimes people die when they have blood transfusion．Later，doctors find that we do not all have the same kind of blood"有的时候人们接受输血后就会死亡，因为血型分为四种，四种之间有的不能混用，否则会致死，由此确定选择C．
71．B，推理判断题，文中提到"I have O-group blood and the doctor told me that I could give blood to anyone else safely"医生告诉我我是O型血，可以给任何人输血，由此确定选择B．
72．A，推理判断题，文中提到"In this way you may stop someone from dying"通过这种方式或许可以阻止失血过多的人死亡，由此确定血库的存在只是确保失血过多的人可以及时的获得血液，由此确定选择A．
73．C，推理判断题，在最后一段中"We call a place where we keep blood a"blood bank"存放血液的地方叫做血库，但并没有指明血库在哪，由此确定选择C．
点评 对于判断对错题，一定要记得首先通读全文，了解文章大意，然后再根据文章关键词，关键句，掌握细节问题，并进行推理判断，再去回答具体的问题．
