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1、2021年天津公共英语考试模拟卷（5）本卷共分为1大题50小题，作答时间为180分钟，总分100分，60分及格。一、单项选择题（共50题，每题2分。每题的备选项中，只有一个最符合题意） 1.Auctions are public sales of goods, conducted by an officially approved auctioneer. He asks the crowd assembled in the auction room to make offers or bids, for the various items on sale. He encourages buye
2、rs to bid higher prices, and finally names the highest bidder as the buyer of the goods. This is called knocking down the goods, for the bidding ends when the auctioneer bangs a small hammer on a table behind which he stands. This is often set on a raised platform called a rostrum. Practically all g
3、oods whose qualities vary are sold by auction. Among these are coffee, hides, skins wool, tea coca, furs, spices, fruit and vegetables and wines. Auctions sales are also usual for land and property, antique furniture, pictures, rare books, old china and similar works of art. The auction rooms at Chr
4、isties and Sothebys in London and New York are world-famous. An auction is usually advertised beforehand and with full particulars of the articles to be sold and where and when they can be viewed by prospective buyers. If the advertisement can not give full details, catalogues are printed, and each
5、group of goods to be together, called a lot, is usually given a number. The auctioneer need not begin with lot 1 and continue in numerical order; he may wait until he registers the fact that certain dealers are in the room and then produce the lots they are likely to be interested in. The auctioneer
6、s services are paid in the form of a percentage of a price the goods are sold for. The auctioneer therefore has a direct interest in pushing up the bidding as high as possible. The auctioneer must know fairly accurately the current market values of the goods be is selling, and he should be acquainte
7、d with regular buyers of such goods. He will not waste time by starting the bidding too low. He will play on the rivalries among his buyers and succeed in getting a high price by encouraging two business competitors to bid against each other. It is largely on his advice that a seller will fix a rese
8、rve price, that is, a price below which the goods cannot be sold. Even the best auctioneers, however, find it difficult to stop a knock-out, whereby dealers illegally arrange before-hand not to bid against each other, but nominate one of themselves as the only bidder, in the hope of buying goods at
9、extremely low price. If such a knock-out comes off, the real auction sales take place privately afterwards among the dealers .The reason why the end of the bidding is called knocking down is that _.Athe auctioneer knocks the buyer downBthe buyer knocks the auctioneer downCthe auctioneer knocks the r
10、ostrum downDthe auctioneer bangs the table with a small hammer 2.Classical physics defines the vacuum as a state of absence :a vacuum is said to exist in a region of space if there is nothing in it. In the quantum field theories that describe the physics of elementary particles, the vacuum becomes s
11、omewhat more complicated. Even in empty space, particles can appear spontaneously as a result of fluctuations of the vacuum. For example, an electron and a positron, or antielectron, can be created out of the void(空间).Particles created in this way have only a fleeting existence; they are annihilated
12、(消亡) almost as soon as they appear, and their presence can never be detected directly. They are called virtual particles in order to distinguish them from real particles, whose lifetimes are not constrained in the same way, and which can be detected. So it is still possible to define the vacuum as a
13、 space that has no real particles in it. One might expect that the vacuum would always be the state of lowest possible energy for a given region of space. If an area is initially empty and a real particle is put into it, the total energy, it seems, should be raised by at least the energy equivalent
14、of the mass of the added particle. A surprising result of some recent theoretical investigations is that this assumption is not invariably tree. There are conditions under which the introduction of a real particle of finite mass into an empty region of space can reduce the total energy. If the reduc
15、tion in energy is great enough, an electron and a positron will be instantly created. Under these conditions the electron and positron are not a result of vacuum fluctuations but are real particles, which exist indefinitely and can be detected. In other words, under these conditions the vacuum is an
16、 unstable state and can decay(衰变)into a state of lower energy; that is one in which real particles are created. The necessary condition for the decay of the vacuum is the presence of an intense electric field. As a result of the decay of the vacuum, the space permeated by such a field can be said to
17、 obtain an electric charge, and it can be called a charged vacuum. The particles that materialize in the space make the charge vacuum is likely to be found in only one place: in the immediate vicinity of a super heavy atomic nucleus(原子核) ,one with about twice as many protons as the heaviest natural
18、nuclei known. A nucleus that large cannot be stable, but it might be possible to assemble one next to a vacuum for long enough to observe the decay of the vacuum. Experiments attempting to achieve this are now under way.According to the passage, the author considers the reduction of energy in an emp
19、ty region of space to which a real particle has been added to beAa well-known process.Ba frequent occurrence.Ca fleeting aberration.Dan unexpected outcome. 3.The Internet raises major issues and challenges for education, not just in China but all over the world. Yet it simply cannot be ignored in te
20、rms of the opportunities and resources that it can offer. We can divide the main issues facing education systems into three groups access, quality and responsibility. Let us consider the Internet in relation to each of them. First, access. Through the Internet, practically the whole world can be bro
21、ught into your classroom. Using e-mail makes it possible to have a class whose members are spread all over the world and who may never meet either the teacher or each other face to face. It can put students in different countries in easy contact. The information resources available are almost limitl
22、ess. With the Internet, students and teachers can access the wisdom, experience, skills, and even guidance of others in a way that was only possible for a very privileged few. Next, quality. The Internet does pose serious problems of quality for education systems. Obviously, there is a lot of materi
23、al on the Internet that no one would want children or students to have uncontrolled access to, but there are other problems which are very difficult to solve. The first is how to handle the sheer quantity of information available, and how to make it manageable. Because anyone can put information on
24、the Internet, and there are no limits on quantity, it can be almost impossible to find exactly the information that one wants. Teachers and students cannot afford to waste time on unsuccessful searching. How can we identify the information which will be most useful without overloading ourselves and
25、our students with unnecessary information How do we select the best information from all that is available This raises the issue of responsibility. There are few editors or quality controllers on the Internet. The ultimate responsibility for selection and judgment falls to the user, whether teacher
26、or student. Teachers, and still less students, are not experts in every field; what we select may not be what we really want, perhaps is old, even wrong. Any profession must take some collective responsibility in resolving these problems. Conscious and deliberate efforts have to be made to share inf
27、ormation between teachers about useful sites and about the best way to use them. Those who have found something useful or of high quality should not keep the information to themselves, but share it as widely as possible. There are many professional discussion groups active on the Internet which aim
28、to do this. Access to them by teachers should be actively encouraged. This will require investment by institutions in giving easy access to the Internet and email to all teachers. Without this investment, educators and ultimately students will be deprived of a vital resource for the development of e
29、ducation in the future.The word institutions (Para. 12, line 2) here probably refers toAcommunities.Bgovernments.Cschools.Dresearching groups. 4.Auctions are public sales of goods, conducted by an officially approved auctioneer. He asks the crowd assembled in the auction room to make offers or bids,
30、 for the various items on sale. He encourages buyers to bid higher prices, and finally names the highest bidder as the buyer of the goods. This is called knocking down the goods, for the bidding ends when the auctioneer bangs a small hammer on a table behind which he stands. This is often set on a r
31、aised platform called a rostrum. Practically all goods whose qualities vary are sold by auction. Among these are coffee, hides, skins wool, tea coca, furs, spices, fruit and vegetables and wines. Auctions sales are also usual for land and property, antique furniture, pictures, rare books, old china
32、and similar works of art. The auction rooms at Christies and Sothebys in London and New York are world-famous. An auction is usually advertised beforehand and with full particulars of the articles to be sold and where and when they can be viewed by prospective buyers. If the advertisement can not gi
33、ve full details, catalogues are printed, and each group of goods to be together, called a lot, is usually given a number. The auctioneer need not begin with lot 1 and continue in numerical order; he may wait until he registers the fact that certain dealers are in the room and then produce the lots t
34、hey are likely to be interested in. The auctioneers services are paid in the form of a percentage of a price the goods are sold for. The auctioneer therefore has a direct interest in pushing up the bidding as high as possible. The auctioneer must know fairly accurately the current market values of t
35、he goods be is selling, and he should be acquainted with regular buyers of such goods. He will not waste time by starting the bidding too low. He will play on the rivalries among his buyers and succeed in getting a high price by encouraging two business competitors to bid against each other. It is l
36、argely on his advice that a seller will fix a reserve price, that is, a price below which the goods cannot be sold. Even the best auctioneers, however, find it difficult to stop a knock-out, whereby dealers illegally arrange before-hand not to bid against each other, but nominate one of themselves a
37、s the only bidder, in the hope of buying goods at extremely low price. If such a knock-out comes off, the real auction sales take place privately afterwards among the dealers .The auctioneer may decide to sell the lot out of order because _.Ahe thinks that some are more valuable than the othersBfrom
38、 the registrations, he knows that certain people will want to buy certain itemsChe fails to give full details of some articlesDhe is not in the world famous auction rooms 5.Classical physics defines the vacuum as a state of absence :a vacuum is said to exist in a region of space if there is nothing
39、in it. In the quantum field theories that describe the physics of elementary particles, the vacuum becomes somewhat more complicated. Even in empty space, particles can appear spontaneously as a result of fluctuations of the vacuum. For example, an electron and a positron, or antielectron, can be cr
40、eated out of the void(空间).Particles created in this way have only a fleeting existence; they are annihilated(消亡) almost as soon as they appear, and their presence can never be detected directly. They are called virtual particles in order to distinguish them from real particles, whose lifetimes are n
41、ot constrained in the same way, and which can be detected. So it is still possible to define the vacuum as a space that has no real particles in it. One might expect that the vacuum would always be the state of lowest possible energy for a given region of space. If an area is initially empty and a r
42、eal particle is put into it, the total energy, it seems, should be raised by at least the energy equivalent of the mass of the added particle. A surprising result of some recent theoretical investigations is that this assumption is not invariably tree. There are conditions under which the introducti
43、on of a real particle of finite mass into an empty region of space can reduce the total energy. If the reduction in energy is great enough, an electron and a positron will be instantly created. Under these conditions the electron and positron are not a result of vacuum fluctuations but are real part
44、icles, which exist indefinitely and can be detected. In other words, under these conditions the vacuum is an unstable state and can decay(衰变)into a state of lower energy; that is one in which real particles are created. The necessary condition for the decay of the vacuum is the presence of an intens
45、e electric field. As a result of the decay of the vacuum, the space permeated by such a field can be said to obtain an electric charge, and it can be called a charged vacuum. The particles that materialize in the space make the charge vacuum is likely to be found in only one place: in the immediate
46、vicinity of a super heavy atomic nucleus(原子核) ,one with about twice as many protons as the heaviest natural nuclei known. A nucleus that large cannot be stable, but it might be possible to assemble one next to a vacuum for long enough to observe the decay of the vacuum. Experiments attempting to ach
47、ieve this are now under way.The authors assertions concerning the conditions that lead to the decay of the vacuum would be most weakened if which of the following occurredAScientists created an electric field next to a vacuum, but found that the electric field was not intense enough to create a char
48、ged vacuum.BScientists assembled a super heavy atomic nucleus next to a vacuum, but found that no virtual particles were created in the vacuums region of space.CScientists assembled a super heavy atomic nucleus next to a vacuum, but found that they could not then detect any real particles in the vacuums region of space.DScientists introduced a virtual electron and a virtual positron into a vacuums region of space, but found that vacuum did not then fluctuate. 6.The Internet raises major issues and challenges for education, not just in China but all over the world. Yet it simply cannot be