[外语类试卷]大学英语六级改革适用(阅读)模拟试卷91及答案与解析.doc
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1、大学英语六级改革适用(阅读)模拟试卷 91及答案与解析 Section C 0 A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or material adversely. Air pollution requires a very flexible definition that permits co
2、ntinuous change. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the healt
3、h aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapour might be considered an air pollutant under certain conditions. Many of the more important air pollutants, such as sulphur oxides, carbon monoxide, and nitrogen oxides, are found
4、in nature. As the earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycles. These reactions serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global
5、basis, nature s output of these compounds dwarfs that resulting from human activities. However, human production usually occurs in a localized area, such as a city. In this localized region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The
6、result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a p
7、ollutant; in fact the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulphur dioxide has detectable health effects at 0.08 parts per million(ppm), which is about 400 times its natural l
8、evel. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm. 1 It can be inferred from the first paragraph that_. ( A) water vapour is an air pollutant in localized areas ( B) the definition of an air pollutant will continue to c
9、hange ( C) a substance becomes an air pollutant only in cities ( D) most air pollutants today can be seen or smelled 2 What effect did the development of earth have on the air pollutants such as carbon monoxide? ( A) Their harm to human activities became more serious. ( B) Their ability to purify ai
10、r was improved a lot. ( C) Their concentrations were changed by chemical reactions. ( D) Their quantities in the air were mainly from human activities. 3 According to the passage, what can we know about human-generated air pollution in cities? ( A) It is the most serious pollution in the environment
11、. ( B) It may overburden the natural system that purifies pollutants. ( C) It will react harmfully with naturally occurring pollutants. ( D) It will damage areas outside the localized regions. 4 The author puts forward the examples of sulphur dioxide and carbon monoxide at last to show that_. ( A) s
12、ulphur dioxide is more dangerous than carbon monoxide ( B) sulphur dioxide is less dangerous than carbon monoxide ( C) the numerical value of noxious chemicals in the air is not the key in defining pollution ( D) it needs a great increase in concentration for noxious chemicals in the air to be pollu
13、tants 5 The passage mainly discusses_. ( A) how gas chemicals become air pollutants ( B) how much damage air pollutants can cause ( C) the definition of an air pollutant ( D) the quantity of compounds added to the atmosphere 5 As a physician who travels quite a bit, I spend a lot of time on planes l
14、istening for that dreaded “Is there a doctor onboard?“ announcement. Ive been called only once for a woman who had merely fainted. But the incident made me curious about how often this kind of thing happens. I wondered what I would do if confronted with a real mid-air medical emergency without acces
15、s to a hospital staff and the usual emergency equipment. So when the New England Journal of Medicine last week published a study about in-flight medical events, I read it with interest. The study estimated that there are an average of 30 in-flight medical emergencies on US flights every day. Most of
16、 them are not grave: fainting, dizziness and hyperventilation are the most frequent complaints. But 13% of them roughly four a day are serious enough to require a pilot to change course. The most common of the serious emergencies include heart trouble(46%), strokes and other neurological problems(18
17、%), and difficulty breathing(6%). Let s face it: plane rides are stressful. For starters, cabin pressures at high altitudes are set at roughly what they would be if you lived at 5000 to 8000 feet above sea level. Most people can tolerate these pressures pretty easily, but passengers with heart disea
18、se may experience chest pains as a result of the reduced amount of oxygen flowing through their blood. Low pressure can also cause the air in body cavities to expand as much as 30%. Again, most people wont notice anything beyond mild stomach cramping. But if you ve recently had an operation, your wo
19、und could open and if a medical device has been implanted in your body a splint, a tracheotomy tube or a catheter it could expand and cause injury. Another common in-flight problem is deep venous thrombosis the so-called economy-class syndrome. When you sit too long in a cramped position, the blood
20、in your legs tends to clot. Most people just get sore calves. But blood clots, left untreated, could travel to the lungs, causing breathing difficulties and even death. Such clots are readily prevented by keeping blood flowing; walk and stretch your legs when possible. Whatever you do, dont panic. T
21、hings are looking up on the in-flight-emergency front. Doctors who come to passengers aid used to worry about getting sued; their fears have lifted somewhat since the 1998 Aviation Medical Assistance Act gave them “good Samaritan“ protection. And thanks to more recent legislation, flights with at le
22、ast one attendant are starting to install emergency medical kits with automated defibrillators to treat heart attacks. Are you still wondering if you are healthy enough to fly? If you can walk 150 ft. or climb a flight of stairs without getting winded, youll probably do just fine. Having a Doctor cl
23、ose by doesn t hurt, either. 6 Strokes and other neurological problems take up about_of the in-flight medical emergencies on US flights. ( A) 0.13 ( B) 0.46 ( C) 0.18 ( D) 0.02 7 The word “grave“(Line 2, Para. 2)may be replaced by_. ( A) slight ( B) emergent ( C) serious ( D) chronical 8 According t
24、o the passage, the expansion of air in body cavities can result in_. ( A) chest pain ( B) heart attack ( C) stomach cramping ( D) difficulty in breathing 9 The deep venous thrombosis usually happens due to_. ( A) the narrow economy class ( B) the great number of economy-class passengers ( C) the pro
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