1、GMAT（ VERBAL）阅读练习试卷 1及答案与解析 1 Caffeine, the stimulant in coffee, has been called “the most widely used psychoactive substance on Earth .” Synder, Daly and Bruns have recently proposed that caffeine affects behavior by countering the activity in (5) the human brain of a naturally occurring chemical c
2、alled adenosine. Adenosine normally depresses neuron firing in many areas of the brain. It apparently does this by inhibiting the release of neurotransmitters, chemicals that carry nerve impulses from one neuron to the next. (10) Like many other agents that affect neuron firing, adenosine must first
3、 bind to specific receptors on neuronal membranes. There are at least two classes of these receptors, which have been designated A1 and A2. Snyder et al propose that caffeine, which is struc- (15) turally similar to adenosine, is able to bind to both types of receptors, which prevents adenosine from
4、 attaching there and allows the neurons to fire more readily than they otherwise would. For many years, caffeines effects have been attri- (20) buted to its inhibition of the production of phosphodi- esterase, an enzyme that breaks down the chemical called cyclic AMP.A number of neurotransmitters ex
5、ert their effects by first increasing cyclic AMP concentra- tions in target neurons. Therefore, prolonged periods at (25) the elevated concentrations, as might be brought about by a phosphodiesterase inhibitor, could lead to a greater amount of neuron firing and, consequently, to behav- ioral stimul
6、ation. But Snyder et al point out that the caffeine concentrations needed to inhibit the production (30) of phosphodiesterase in the brain are much higher than those that produce stimulation. Moreover, other com- pounds that block phosphodiesterases activity are not stimulants. To buttress their cas
7、e that caffeine acts instead by pre- (35) venting adenosine binding, Snyder et al compared the stimulatory effects of a series of caffeine derivatives with their ability to dislodge adenosine from its receptors in the brains of mice. “In general,” they reported, “the ability of the compounds to comp
8、ete at the receptors (40) correlates with their ability to stimulate locomotion in the mouse; i.e., the higher their capacity to bind at the receptors, the higher their ability to stimulate locomo- tion.” Theophylline, a close structural relative of caffeine and the major stimulant in tea, was one o
9、f the most (45) effective compounds in both regards. There were some apparent exceptions to the general correlation observed between adenosine-receptor binding and stimulation. One of these was a compound called 3-isobuty1-1-methylxanthine(IBMX), which bound very (50) well but actually depressed mou
10、se locomotion. Snyder et al suggest that this is not a major stumbling block to their hypothesis. The problem is that the compound has mixed effects in the brain, a not unusual occurrence with psychoactive drugs. Even caffeine, which is generally (55) known only for its stimulatory effects, displays
11、 this property, depressing mouse locomotion at very low concentrations and stimulating it at higher ones. 1 The primary purpose of the passage is to_ （ A） discuss a plan for investigation of a phenomenon that is not yet fully understood （ B） present two explanations of a phenomenon and reconcile the
12、 differences between them （ C） summarize two theories and suggest a third theory that overcomes the problems encountered in the first two （ D） describe an alternative hypothesis and provide evidence and arguments that support it （ E） challenge the validity of a theory by exposing the inconsistencies
13、 and contradictions in it 2 According so Snyder et al, caffeine differs from adenosine in that caffeine_ （ A） stimulates behavior in the mouse and in humans, whereas adenosine stimulates behavior in humans only （ B） has mixed effects in the brain, whereas adenosine has only a stimulatory effect （ C）
14、 increases cyclic AMP concentrations in target neurons, whereas adenosine decreases such concentrations （ D） permits release of neurotransmitters when it is bound to adenosine receptors, whereas adenosine inhibits such release （ E） inhibits both neuron firing and the production of phosphodiesterase
15、when there is a sufficient concentration in the brain, whereas adenosine inhibits only neuron firing 3 In response to experimental results concerning IBMX, Snyder et al contended that it is not uncommon for psychoactive drugs to have_ （ A） mixed effects in the brain （ B） inhibitory effects on enzyme
16、s in the brain （ C） close structural relationships with caffeine （ D） depressive effects on mouse locomotion （ E） the ability to dislodge caffeine from receptors in the brain 4 According to Snyder et al, all of the following compounds can bind to specific receptors in the brain EXCEPT_ （ A） IBMX （ B
17、） caffeine （ C） adenosine （ D） theophylline （ E） phosphodiesterase 5 Snyder et al suggest that caffeines ability to bind to A1 and A2 receptors can be at least partially attributed to which of the following? （ A） The chemical relationship between caffeine and phosphodiesterase （ B） The structural re
18、lationship between caffeine and adenosine （ C） The structural similarity between caffeine and neurotransmitters （ D） The ability of caffeine to stimulate behavior （ E） The natural occurrence of caffeine and adenosine in the brain 6 The author quotes Snyder et al in lines 38-43 most probably in order
19、 to_ （ A） reveal some of the assumptions underlying their theory （ B） summarize a major finding of their experiments （ C） point out that their experiments were limited to the mouse （ D） indicate that their experiments resulted only in general correlations （ E） refute the objections made by supporter
20、s of the older theory 7 Archaeology as a profession faces two major prob- lems. First, it is the poorest of the poor. Only paltry sums are available for excavating and even less is avail- able for publishing the results and preserving the sites (5) once excavated. Yet archaeologists deal with pricel
21、ess objects every day. Second, there is the problem of illegal excavation, resulting in museum-quality pieces being sold to the highest bidder. I would like to make an outrageous suggestion that (10) would at one stroke provide funds for archaeology and reduce the amount of illegal digging. I would
22、propose that scientific archeological expeditions and govern- mental authorities sell excavated artifacts on the open market. Such sales would provide substantial funds for (15) the excavation and preservation of archaeological sites and the publication of results. At the same time, they would break
23、 the illegal excavators grip on the market, thereby decreasing the inducement to engage in illegal activities. (20) You might object that professionals excavate to acquire knowledge, not money. Moreover, ancient arti- facts are part of our global cultural heritage, which should be available for all
24、to appreciate, not sold to the highest bidder. I agree. Sell nothing that has unique (25) artistic merit or scientific value. But, you might reply, everything that comes our of the ground has scientific value. Here we part company. Theoretically, you may be correct in claiming that every artifact ha
25、s potential scien- tific value. Practically, you are wrong. (30) I refer to the thousands of pottery vessels and ancient lamps that are essentially duplicates of one another. In one small excavation in Cyprus, archaeologists recently uncovered 2,000 virtually indistinguishable small jugs in a single
26、 courtyard, Even precious royal seal impressions (35) known as/melekh handles have been found in abun- dance-more than 4,000 examples so far. The basements of museums are simply not large enough to store the artifacts that are likely to be discov- ered in the future. There is not enough money even t
27、o (40) catalogue the finds; as a result, they cannot be found again and become as inaccessible as if they had never been discovered. Indeed, with the help of a computer, sold artifacts could be more accessible than are the pieces stored in bulging museum basements. Prior to (45) sale, each could be
28、photographed and the list of the purchasers could be maintained on the computer A purchaser could even be required to agree to return the piece if it should become needed for scientific purposes. It would be unrealistic to suggest that illegal digging (50) would stop if artifacts were sold on the op
29、en market. But the demand for the clandestine product would be substantially reduced. Who would want an unmarked pot when another was available whose provenance was known, and that was dated stratigraphically by the professional archaeologist who excavated it? 7 The primary purpose of the passage is
30、 to propose_ （ A） an alternative to museum display of artifacts （ B） a way to curb illegal digging while benefiting the archaeological profession （ C） a way to distinguish artifacts with scientific value from those that have no such value （ D） the governmental regulation of archaeological sites （ E）
31、 a new system for cataloguing duplicate artifacts 8 The author implies that all of the following statements about duplicate artifacts are true EXCEPT_ （ A） A market for such artifacts already exists. （ B） Such artifacts seldom have scientific value. （ C） There is likely to be a continuing supply of
32、such artifacts. （ D） Museums are well supplied with examples of such artifacts. （ E） Such artifacts frequently exceed in quality those already catalogued in museum collections. 9 Which of the following is mentioned in the passage as a disadvantage of storing artifacts in museum basements? （ A） Museu
33、m officials rarely allow scholars access to such artifacts. （ B） Space that could be better used for display is taken up for storage. （ C） Artifacts discovered in one excavation often become separated from each other. （ D） Such artifacts are often damaged by variations in temperature and humidity. （
34、 E） Such artifacts often remain uncatalogued and thus cannot be located once they are put in storage. 10 The author mentions the excavation in Cyprus (lines 31-34) to emphasize which of the following points? （ A） Ancient lamps and pottery vessels are less valuable, although more rare, than royal sea
35、l impressions. （ B） Artifacts that are very similar to each other present cataloguing difficulties to archaeologists. （ C） Artifacts that are not uniquely valuable, and therefore could be sold, are available in large quantities. （ D） Cyprus is the most important location for unearthing large quantit
36、ies of salable artifacts. （ E） Illegal sales of duplicate artifacts are wide-spread, particularly on the island of Cyprus. 11 The authors argument concerning the effect of the official sale of duplicate artifacts on illegal excavation is based on which of the following assumptions? （ A） Prospective
37、purchasers would prefer to buy authenticated artifacts. （ B） The price of illegally excavated artifacts would rise. （ C） Computers could be used to trace sold artifacts. （ D） Illegal excavators would be forced to sell only duplicate artifacts. （ E） Money gained from selling authenticated artifacts c
38、ould be used to investigate and prosecute illegal excavators. 12 The author anticipates which of the following initial objections to the adoption of his proposal? （ A） Museum officials will become unwilling to store artifacts. （ B） An oversupply of salable artifacts will result and the demand for th
39、em will fall. （ C） Artifacts that would have been displayed in public places will be sold to private collectors. （ D） Illegal excavators will have an even larger supply of artifacts for resale. （ E） Counterfeiting of artifacts will become more commonplace. 13 Federal efforts to aid minority business
40、es began in the 1960s when the Small Business Administration (SBA) began making federally guaranteed loans and govern- ment-sponsored management and technical assistance (5) available to minority business enterprises. While this program enabled many minority entrepreneurs to form new businesses, the
41、 results were disappointing, since managerial inexperience, unfavorable locations, and capital shortages led to high failure rates. Even 15 (10) years after the program was implemented, minority business receipts were not quite two percent of the national economys total receipts. Recently federal po
42、licymakers have adopted an approach intended to accelerate development of the (15) minority business sector by moving away from directly aiding small minority enterprises and toward supporting larger, growth-oriented minority firms through interme- diary companies. In this approach, large corporatio
43、ns participate in the development of successful and stable (20) minority businesses by making use of government- sponsored venture capital. The capital is used by a participating company to establish a Minority Enterprise Small Business Investment Company or MESBIC. The MESBIC then provides capital
44、and guidance to minority (25) businesses that have potential to become future suppliers or customers of the sponsoring company. MESBICs are the result of the belief that providing established firms with easier access to relevant manage- ment techniques and more job-specific experience, as (30) well
45、as substantial amounts of capital, gives those firms a greater opportunity to develop sound business founda- tions than does simply making general management experience and small amounts of capital available. Further, since potential markets for the minority busi- (35) nesses already exist through t
46、he sponsoring companies, the minority businesses face considerably less risk in terms of location and market fluctuation. Following early financial and operating problems, sponsoring corporations began to capitalize MESBICs far above (40) the legal minimum of $500,000 in order to generate sufficient
47、 income and to sustain the quality of manage- ment needed. MESBICc are now emerging as increas- ingly important financing sources for minority enter- prises. (45) Ironically, MESBIC staffs, which usually consist of Hispanic and Black professionals, tend to approach investments in minority firms more
48、 pragmatically than do many MESBIC directors, who are usually senior managers from sponsoring corporations. The latter (50) often still think mainly in terms of the “social responsi- bility approach” and thus seem to prefer deals that are riskier and less attractive than normal investment criteria w
49、ould warrant. Such differences in viewpoint have pro- duced uneasiness among many minority staff members, (55) who feel that minority entrepreneurs and businesses should be judged by established business considerations. These staff members believe their point of view is closer to the original philosophy of MESBICs and they are concerned that, unless a more prudent course is fol- lowed, MESBIC directors may revert to policies likely to re-create the disappointing results of the original SBA approach. 13 Which of the following best states the cent
