[外语类试卷]大学英语四级模拟试卷337及答案与解析.doc
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1、大学英语四级模拟试卷 337及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed 30 minutes to write a composition on campus love. You should write at least 120 words following the outline given below in Chinese: 1. 对于大学在校本科生谈恋爱的现象,不同的人有不同的看法 。 2你的观点。 二、 Part II Reading Comprehension (Skimming a
2、nd Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-7, mark: Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the statement contradict
3、s the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Bird Flu The H5N1 strain of influenza(H5N1 类禽流感 )-often referred to as bird flu-was first known to have spread from chickens to humans in 1997. Since 2004 it has attacked Asian poultry farms
4、(家禽饲养所 ), and had a 7% death rate in the first 70 people who were known to have been infected. Health authorities fear this strain, or its descendents (变种 ), could cause a fatal new flu with the potential to kill billions. Flu has been a regular disaster of humanity for thousands of years. The flu v
5、iruses are a large family, each possessing a mere 10 genes encoded in RNA (核糖核酸 ). All of the 16 known groups come first from water birds, especially ducks and gulls (鸥 ). The virus is well adapted to their immune systems, and does not usually make them very sick. This leaves the animals free to mov
6、e around and spread the virus. Violent virus But every now and then a bird flu virus is transmitted to all animal whose immune system the virus is not adapted to. If the bird flu from a forest bird spreads to chickens, it causes an average disease but can readily change to a more severe strain. Just
7、 such a strain of HSN1 flu has hit large chicken farms in East Asia. The situation is serious because, in 1997, scientists found for the first time that H5 flu is capable of infecting humans. It was found in 18 people, six of whom died. All the poultry in Hong Kong were destroyed to stop the threat.
8、 But it continued to circulate, especially in China. There were further human cases in China in 2003. Then in early 2004 Vietnam (越南 ) reported widespread poultry outbreaks and some human cases. Cambodia (柬埔寨 ) and Thailand denied the outbreaks in the beginning but admitted the fact later. So did Ch
9、ina. A mass poultry selection stopped the outbreaks by March 2004, by which time 23 people had died. But the virus went on, most probably in ducks. But scientists think that we should not blame its persistence and spread in the region all on wild birds. The outbreaks started again in summer 2004, an
10、d by mid-April 2005 had caused a total of 51 human deaths, all in Thailand and Vietnam. Making the jump The two or three flu virus families that have made the jump to humans mostly cause slight disease, because they have adapted to our immune systems. A yearly winter flu suffers most of the world. B
11、ut it is not totally benign (良性的 ). About 700,000 people around the world die of it each year, mainly the very old, very young and the weak. Common flu vaccines(疫苗 ) are increasing in popularity, although flu evolves so fast that we need new flu vaccines every year. In 2004 an unexpected shortage of
12、 vaccine in the US indicated the weakness of the vaccine supply, which is produced by very few manufacturers. As New Scientist predicted, it took great efforts to limit available supplies to those most at risk of serious illness, preventing extra deaths. But flu is most deadly when it first makes th
13、e jump to people because the virus had no opportunity to adapt itself to our immune systems. H5N1 has continued to infect humans as the outbreak in poultry has increased, with an apparently high death rate. It has so far been hard to infect human beings, and has not spread readily between people. If
14、 this viral strain should acquire that ability of attacking us, it could become a lethal pandemic (流行性疾病 )-the name for a wide-spread disease that spreads worldwide. Deadly widespread In 1918, a virulent (有毒菌株 ) flu strain appeared in humans and killed 50 million people within a few months. There ha
15、ve also been two less catastrophic(悲惨的 ) pandemics. The so-called “Asian“ flu of 1957 caused between one and four million deaths, while 1968s “Hong Kong“ flu with about half the estimated deadliness of the Asian flu-caused one to two million deaths. Both of these were human flu viruses which had rec
16、ombined with bird flu viruses. The 1957 strain was nearly released by accident in 2005. Virologists generally agree that we are due for another pandemic. So they are very worried about H5N1, because-like the 1918 event-it seems to be evolving to become more deadly to mammals(哺乳动物 ). This is largely
17、in China and, possibly, as New Scientist revealed, in vaccinated chickens. It could evolve into a potential pandemic that way, or by recombining with human flu, especially as most people in the Far East are not vaccinated against ordinary flu strains. Mitigation (缓解 ) measures Fortunately we can mak
18、e vaccines for the H5NI strain, although our ability to get them tested and manufactured in time for a pandemic is in doubt. Once an effective vaccine is produced, yet another defense would be against it swiftly. If either aspect of that process should fail, the only backup would be antiviral (抗病毒药
19、) drugs. A few new ones are on the way, but existing drugs are in short supply. If the flu virus changes genetically, it may become less deadly. However, there is no reason to think this will happen, and a highly infectious virus with a 70% death rate is a terrifying prospect, particularly given the
20、 speed of modern international travel.There is also a chance that it could evolve into a completely new disease, which we could fail to examine before it spreads. Even if H5 does not lead to the next pandemic, its cousins H7 and H9 could. H7 is present in the same region and also infected large numb
21、ers of Dutch people in an outbreak in 2003. Although it caused few symptoms (症状 ), and only one death, it is possible that such a poultry virus could cross-breed with a human flu, making it even more dangerous. Some scientists are not willing to wait and see. They are trying to breed contagiousness
22、(传染性 ) into H5N1 to see if it is likely to happen. Others are breeding replicas (复制品 ) of the 1918 virus-from samples recovered from victims-to see just what made it so deadly. But some feel that those experiments, because of the potential for escape from the lab, put us at as much risk as the natur
23、al evolution of the virus. Debora Mackenzie, 6 May 2005 2 Cancer is a potential threat to human beings. ( A) Y ( B) N ( C) NG 3 The virus of flu is well adapted to immune systems of water birds, and does not usually make them very sick. ( A) Y ( B) N ( C) NG 4 Scientists think that we should blame t
24、he virus of flu all on wild birds. ( A) Y ( B) N ( C) NG 5 So far H5N1 can easily infect human beings, and spreads readily between people. ( A) Y ( B) N ( C) NG 6 H5N1 could evolve into a potential pandemic that way, or by recombining with human flu. ( A) Y ( B) N ( C) NG 7 Fortunately we can make v
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- 外语类 试卷 大学 英语四 模拟 337 答案 解析 DOC
