[外语类试卷]专业英语八级(阅读)模拟试卷109及答案与解析.doc
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1、专业英语八级(阅读)模拟试卷 109及答案与解析 SECTION A MULTIPLE-CHOICE QUESTIONS In this section there are several passages followed by fourteen multiple-choice questions. For each multiple-choice question, there are four suggested answers marked A , B, C and D. Choose the one that you think is the best answer. 0 (1)Ho
2、w living creatures evolve has been pretty well understood for the past 150 years. How they came to exist in the first place, though, remains a mystery. Part of the reason for this mystery is that subsequent evolution has done a good job of erasing the evidence. But not a complete one. Some features
3、are shared by all organisms, and may thus go back to the beginning of life. And one of the most bizarre of these features is that a lot of the molecules of which life is made are left-handed. (2)A left-handed molecule is one that causes polarized light to rotate to the left(i.e., anticlockwise). Mos
4、t molecules which behave this way have a right-handed equivalent that is, in its arrangement of atoms, their mirror image. Ordinary chemical processes cannot tell the difference between the two forms, so they are usually equally abundant. But the enzymes that govern biochemistry are such precise too
5、ls that, often, only one-handedness is acceptable. In the case of amino acids, the subunits of which proteins are made, the acceptable form is the sinister one. Many people feel that understanding why this is so would illuminate the origin of life and two groups of researchers, pursuing separate lin
6、es of enquiry, have come up with what may be the pieces of the jigsaw. (3)One further puzzle is that the amino acids found in meteorites(which are assumed to be similar to those of the primitive Earth)have been modified by a process called methylation into a form that is biologically useless. Nevert
7、heless, since such methylated amino acids are the starting point, it is where Ronald Bres-low and his student Mindy Levine, who work at Columbia University, started. (4)A couple of years ago they revealed the first piece of the jigsaw when they found that an initial imbalance in favor of left-handed
8、 methylated amino acids in a solution can be amplified by repeated evaporation. During evaporation, the left-and right-handed molecules mate up and fall out of solution, leaving a left-handed excess. A mere two cycles of evaporation can push a starting ratio that is just 1% in favor of the left to o
9、ne that is 90% left-handed. (5)Now, as Dr. Breslow has revealed to a meeting of the American Chemical Society, in New Orleans, Ms. Levine has discovered a process that favors the production of left-handed biologically active amino acids. The presence of copper in solutions that contain the chemical
10、precursors of amino acids, together with left-handed methylated amino acids to seed the reaction, gives amino-acid formation a sinister bias. When Ms. Levine made an amino acid called phenylalanine this way she got 37% more of me left-handed form than the right-handed. With another, valine, the exce
11、ss was 23% and with alanine, 20%. (6)The connection between the two pieces of work is that the left-handed methylated amino acids required to seed the second could have been provided by the evaporative process of the first if, of course, a slightly biased supply of them had previously existed. (7)Th
12、is is where Sandra Pizzarello of Arizona State University comes in. She has shown that the methylated amino acids found in meteorites do, indeed, have a bias of 1% or more in favor of the left-handed, suggesting that methylated amino acids kicking around on the primitive Earth would have shared a si
13、milar bias. (8)The mistake previous researchers made, therefore, was thinking of the methylated amino acids of meteorites as ingredients of life. Actually, if this work is pointing in the right direction, they were merely seeds. Taken together, these results argue that life formed in places with a l
14、ot of evaporation going on(suggesting heat)and a significant amount of copper present. This is speculation, of course, but it favors the idea that living things were created in land-locked ponds, rather than at sea, and probably in a volcanic environment.(Volcanic heat would drive the chemical react
15、ions, as well as causing lots of evaporation.)It also suggests that biochemical left-handedness confers no selective advantage. What makes meteoritic amino acids left-handed has yet to be discovered. But it seems just a matter of chance that the living world is sinister. 1 What can be inferred from
16、the results of the studies by Ronald Breslow and Mindy Levine? ( A) Repeated evaporation pushes the right-handed molecules out completely. ( B) The simple presence of copper in the solutions gives amino-acid formation a sinister bias. ( C) The result of the first study has seeded the reaction of the
17、 second study. ( D) The two pieces of work connect in that they both created left-handed amino acid. 2 Sandra Pizzarello suggests that methylated amino acids found in meteorites _. ( A) are ingredients of life ( B) have a bias for left-handedness ( C) are the origin of life ( D) have the same bias a
18、s the ones on the primitive Earth 3 From the description in the passage, we learn that _. ( A) evidence of evolution has been completely erased, leaving the origin of life a mystery ( B) most of enzymes that govern biochemistry are left-handed ( C) the results point out that the methylated amino aci
19、ds of meteorites are the seeds of life ( D) the results argue that evaporation and copper are important in the formation of life 3 (1)Too often, investors focus on figures that supposedly offer insight into a companys performance without shedding light on how it actually makes its money. (2)Graphic-
20、design and printing-services company VistaPrint is a case in point. Investors have pushed the shares down over the past month because the companys most recent quarterly results raised concerns about slowing revenue growth and narrowing gross margins. (3)But on that score, investors may be worrying a
21、bout the wrong issue: VistaPrint appears to generate a big portion of its operating profit from fees it receives for “referring“ customers to outside parties that “offer“ rewards programs. (4)That calls into question whether the stock, even after its recent fall, deserves to trade at 20 times expect
22、ed earnings for the fiscal year ending in June 2009, according to estimates from Thomson Reuters. (5)VistaPrints customers often dont realize that they are purchasing the referred services. The services are offered through a screen that pops up at the end of the VistaPrint buying process. That scree
23、n purports to offer the customer $10 off their most recent purchase. But customers who sign up for this are actually enrolling in a program that charges them $14.95 a month for what are supposed to be discounts on amusement parks and movies, among other things. (6)In a statement, VistaPrint said, “W
24、e dont trick our customers into a service that they dont want. Customers are smarter than that. We go to great lengths to ensure that only those customers that want that particular service or offering pay for that service or offering.“ (7)The company declined to say what portion of operating profit
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- 外语类 试卷 专业 英语 阅读 模拟 109 答案 解析 DOC
