题目内容
12．Carbon monoxide（一氧化碳） poisoning kills and injures many people and animals around the world．The gas has been a problem since people first began burning fuels to cook food or to create heat．It is a problem in all parts of the world that experience cold weather．Carbon monoxide is called the silent killer because people do not know it is in the air．The gas has no color．It has no taste．It has no smell．It does not cause burning eyes．And it does not cause people to cough．But it is very deadly．It robs the body of its ability to use oxygen．
Carbon monoxide decreases the ability of the blood to carry oxygen to body tissues．It does this by linking with the blood．When the gas links with the blood，the blood is no longer able to carry oxygen to the tissues that need it．
Damage to the body can begin very quickly from large amounts of carbon monoxide．How quickly this happens depends on the length of time a person is breathing the gas and the amount of the gas he or she breathes in．
Carbon monoxide poisoning has warning signs．But people have to be awake to recognize them．Small amounts of the gas will cause a person's head to hurt．He or she may begin to feel tired．The person may feel sick．The room may appear to be turning around．The person may have trouble thinking clearly．People develop severe head pains as the amount of the gas continues to enter their blood．They will begin to feel very tired and sleepy．They may have terrible stomach pains．
Medical experts say carbon monoxide affects people differently．For example，a small child will experience health problems or die much quicker than an adult will．The general health of the person or his or her age can also be important．An older adult with health problems may suffer the effects of carbon monoxide more quickly than a younger person with no health problems．People with heart disease may suffer chest pains．They may begin to have trouble breathing．
12．Why is carbon monoxide called the silent killer？B
A．Because it tastes and smells good．
B．Because it is not easily noticed．
C．Because it kills and injures people．
D．Because it always harms people．
13．How does carbon monoxide harm people？D
A．It makes people's blood unable to move．
B．It decreases the amount of blood in the body．
C．It makes body tissues full of blood．
D．It makes the blood less able to carry oxygen．
14．When people breathe in small amounts of the gas，they mayA．
A．feel a little dizzy
B．suffer a severe headache
C．go around in the room
D．have a terrible stomachache
15．Which of the following about carbon monoxide poisoning is true？C
A．Adults are affected more seriously than children．
B．Young people are more severely affected than old people．
C．People in poor health may have severer consequences．
D．People with heart problems only suffer from chest pains．
分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了关于一氧化碳使人中毒的原理和现象，警告读者要小心一氧化碳中毒．
解答 12．B．细节理解题．根据第二段Carbon monoxide is called the silent killer because people do not know it is in the air．The gas has no color．It has no taste可知一氧化碳被称为无声杀手因为它不容易被注意到；故选B．
13．D．细节理解题．根据第三段Carbon monoxide decreases the ability of the blood to carry oxygen to body tissues．It does this by linking with the blood可知一氧化碳使血液输送氧气的能力下降；故选D．
14．A．细节理解题．根据第四段Small amounts of the gas will cause a person's head to hurt．He or she may begin to feel tired．The person may feel sick．The room may appear to be turning around可知当人们吸入少量的气体时，他们可能觉得有点晕；故选A．
15．C．推理判断题．根据最后一段An older adult with health problems may suffer the effects of carbon monoxide more quickly than a younger person with no health problems．People with heart disease may suffer chest pains．They may begin to have trouble breathing可知身体不好的人一氧化碳中毒可能会有更严重的后果；故选C．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
