GMAT考试-GWD-CR解析-EXPLAIN

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GWD-5-Q8:
When a new restaurant, Martin’s Cafe, opened in Riverville last year, many people predicted that business at the Wildflower Inn, Riverville’s only other restaurant, would suffer from the competition.  Surprisingly, however, in the year since Martin’s Cafe opened, the average number of meals per night served at the Wildflower Inn has increased significantly.

Which of the following, if true, most helps to explain the increase?

A.        Unlike the Wildflower Inn, Martin’s Cafe serves considerably more meals on weekends than it does on weekdays.以偏概全
B.        Most of the customers of Martin’s Cafe had never dined in Riverville before this restaurant opened, and on most days Martin’s Cafe attracts more customers than it can seat.
C.        The profit per meal is higher, on average, for meals served at Martin’s Cafe than for those served at the Wildflower Inn.
D.        The Wildflower Inn is not open on Sundays, and therefore Riverville residents who choose to dine out on that day must either eat at Martin’s Cafe or go to neighboring towns to eat.无关选项！当时看反了
E.        A significant proportion of the staff at Martin’s Cafe are people who formerly worked at the Wildflower Inn and were hired away by the owner of Martin’s Cafe.[B]
B说M店就餐的人在M店开张之前大多都没在R地吃过饭（说明M的开张增加了总的吃饭人数），而且M店总是有人抢不到位置吃饭（说明增加人数有部分没吃到饭）——》只好到W店去吃了

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GWD-5-Q16:
Maize contains the vitamin niacin, but not in a form the body can absorb.  Pellagra is a disease that results from niacin deficiency.  When maize was introduced into southern Europe from the Americas in the eighteenth century, it quickly became a dietary staple, and many Europeans who came to subsist primarily on maize developed pellagra（指因为欧洲人常吃M，但是M里面的Niacin不能被吸收. ）Pellagra was virtually unknown at that time in the Americas（在美国没有P病）, however, even among people who subsisted primarily on maize.

Which of the following, if true, most helps to explain the contrasting incidence of pellagra described above?

A.        Once introduced into southern Europe, maize became popular with landowners because of its high yields relative to other cereal crops.
B.        Maize grown in the Americas contained more niacin than maize grown in Europe did.
C.        Traditional ways of preparing maize in the Americas convert maize’s niacin into a nutritionally useful form.
D.        In southern Europe many of the people who consumed maize also ate niacin-rich foods.
E.        Before the discovery of pellagra’s link with niacin, it was widely believed that the disease was an infection that could be transmitted from person to person.

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GWD-5-Q33:
Wolves generally avoid human settlements.  For this reason, domestic sheep, though essentially easy prey for wolves, are not usually attacked by them.  In Hylantia prior to 1910, farmers nevertheless lost considerable numbers of sheep to wolves each year.  Attributing this to the large number for wolves, in 1910 the government began offering rewards to hunters for killing wolves.  From 1910 to 1915, large numbers of wolves were killed.  Yet wolf attacks on sheep increased significantly.
狼数量减少，domestic羊反而减少了
Which of the following, if true, most helps to explain the increase in wolf attacks on sheep?

A.        Populations of deer and other wild animals that wolves typically prey on increased significantly in numbers from 1910 to 1915.
B.        Prior to 1910, there were no legal restrictions in Hylantia on the hunting of wolves.
C.        After 1910 hunters shot and wounded a substantial number of wolves, thereby greatly diminishing these wolves’ ability to prey on wild animals.（所以狼只好去吃容易捕食的家羊了）
D.        Domestic sheep are significantly less able than most wild animals to defend themselves against wolf attacks.（是C的原因，但不是上述现象的直接原因）
E.        The systematic hunting of wolves encouraged by the program drove many wolves in Hylantia to migrate to remote mountain areas uninhabited by humans.[C]

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GWD-5-Q38:
Nitrogen dioxide is a pollutant emitted by automobiles.  Catalytic converters, devices designed to reduce nitrogen dioxide emissions, have been required in all new cars in Donia since 1993, and as a result, nitrogen dioxide emissions have been significantly reduced throughout most of the country.  Yet although the proportion of new cars in Donia’s capital city has always been comparatively high, nitrogen dioxide emissions there have showed only an insignificant decline since 1993.
1993年起Donia所有新车要求CC。Donia大多数地方因此尾气排放减少。但是在D的首都，虽然新车比例很高，但是1993年以来尾气排放没有明显减低
Which of the following, if true, most helps to explain the insignificant decline in nitrogen dioxide emissions in Donia’s capital city?

A.        More of the cars in Donia’s capital city were made before 1993 than after 1993.
B.        The number of new cars sold per year in Donia has declined slightly since 1993.
C.        Pollutants other than nitrogen dioxide that are emitted by automobiles have also been significantly reduced in Donia since 1993.
D.        Many Donians who own cars made before 1993 have had catalytic converters installed in their cars.
E.        Most car trips in Donia’s capital city are too short for the catalytic converter to reach its effective working temperature.[E]（比如城市交通拥堵，使车子无法长距离启动，一开一停，无法达到处理废弃的功效）
A错：比如1993年前11万辆，1993后10万辆。那末要求1993年后的车装CONVERTER，肯定污染会明显减少。A解释不了原文的现象

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GWD-8-Q33***: 注意找同一名词下的不同现象
In order to withstand tidal currents, juvenile horseshoe crabs frequently burrow in the sand. Such burrowing discourages barnacles from clinging to their shells. When fully grown, however, the crabs can readily withstand tidal currents without burrowing, and thus they acquire substantial populations of barnacles. Surprisingly, in areas where tidal currents are very weak, juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow.

Which of the following, if true, most helps to explain the surprising finding?
关键，找影响Barnacle的因素。
1 Burrow，越埋越不会有Barnacles。
2 grown了，不埋，Barnacles多
3 Barnacles和shell
A. Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.与画线部分矛盾
B. Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
C. The strength of the tidal currents in a given location varies widely over the course of a day.
D. A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
E. Until they are fully grown, horseshoe crabs shed their shells and grow new ones several times a year.[E]
这是解释矛盾题（或解释现象），要先找到矛盾（或奇怪现象）。
奇怪现象：Such burrowing discourages barnacles from clinging to their shells即一般juvenile horseshoe crabs 会附着 barnacles 。但是， juvenile horseshoe crabs are found not to have significant barnacle populations, even though they seldom burrow（这排除BURROW使它们没有附着barnacle的原因）。所以你要找另外原因解释 found not to have significant barnacle 。E的意思为 juvenile horseshoe crabs （ Until they are fully grown指在他们长大前）一年有几次脱旧壳，长新壳。所以上面的barnacle都给脱掉了，当然没发现 barnacle 。
排除法：A和原文第二句话矛盾，Tidal currents 无法去掉 crabs 的 barnacles。

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GWD-9-Q12:
A mosquito bite can transmit to a person the parasite that causes malaria, and the use of mosquito nets over children’s beds can significantly reduce the incidence of malarial infection for children in areas where malaria is common. Yet public health officials are reluctant to recommend the use of mosquito nets over children’s beds in such areas.
蚊网虽然能够减少疟疾感染小孩，但是健康专家不推荐小孩使用蚊网
Which of the following, if true, would provide the strongest grounds for the public health officials’ reluctance?

A. Early exposure to malaria increases the body’s resistance to it and results in a lesser likelihood of severe life-threatening episodes of malaria.
B. Mosquito bites can transmit to people diseases other than malaria. 削弱
C. Mosquito nets provide protection from some insect pests other than mosquitoes.削弱
D. Although there are vaccines available for many childhood diseases, no vaccine has been developed that is effective against malaria.无关
E. The pesticides that are most effective against mosquitoes in regions where malaria is common have significant detrimental effects on human health.[A]无关

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GWD-9-Q16:
A diet high in saturated fats increases a person’s risk of developing heart disease. Regular consumption of red wine reduces that risk. Per-capita consumption of saturated fats is currently about the same in France as in the United States, but there is less heart disease there than in the United States because consumption of red wine is higher in France. The difference in regular red-wine consumption has been narrowing, but no similar convergence in heart-disease rates has occurred.
红酒降低心脏病并发危险。
美国比法国和红酒的少，美国比法国心脏病多。
红酒消费差距在减少，心脏病并发率没有变化。
Which of the following, if true, most helps to account for the lack of convergence noted above?

A. Consumption of saturated fats is related more strongly to the growth of fatty deposits on artery walls, which reduce blood flow to the heart, than it is to heart disease directly.
B. Over the past 30 years, per-capita consumption of saturated fats has remained essentially unchanged in the United States but has increased somewhat in France.
C. Reports of the health benefits of red wine have led many people in the United States to drink red wine regularly. 前提的原因
D. Cigarette smoking, which can also contribute to heart disease, is only slightly more common in France than in the United States. 没有解释为何美国仍旧比法国心脏病多
E. Regular consumption of red wine is declining dramatically among young adults in France, and heart disease typically does not manifest itself until middle age.[E]
如果如B所说，即法国的per-capita consumption of saturated fats 增加，则heart disease会增加，合美国的CONVERGENCE就有可能，解释不了lack of convergence noted。
原文给两个规律：FAT高HEART DISEASE也高。WINE低HEART DISEASE也低。
过去：法国（FAT一样，WINE高，HEART DISEASE低）
           美国（FAT一样，WINE低，HEART DISEASE高）
现在：WINE的差别已缩小，却HEART DISEASE没缩小。
B说美国的FAT没变，法国的FAT增加点，既然法国的FAT增加，HEART DISEASE也应增加，它和美国在HEART DISEASE方面的差距应缩小。但原文要你解释的是没缩小。

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GWD-11-Q27:
Mayor:  Migrating shorebirds stop at our beach just to feed on horseshoe-crab eggs, a phenomenon that attracts tourists.  To bring more tourists, the town council plans to undertake a beach reclamation project to double the area available to crabs for nesting.

Birdwatcher:  Without a high density of crabs on a beach, migrating shorebirds will go hungry because shorebirds only eat eggs that a crab happens to uncover when it is digging its own nest.

Which of the following, if true, would provide the mayor with the strongest counter to the birdwatcher’s objection?

A.        Every year a certain percentage of crabs are caught by fishermen as bait for eel traps.
B.        Horseshoe crabs are so prolific that given favorable circumstances their numbers increase rapidly.
C.        On average, tourists who come to the town in order to watch birds spend more money there than tourists who come for other purposes.
D.        The additional land made available by the reclamation project will give migrating shorebirds more space.
E.        Some of the migrating shorebirds make only one stop during their migration form South America to Canada.

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GWD-12-Q22*
Denoma, a major consumer-electronics maker, had a sizeable decline in sales revenue for its most recent fiscal year.  This result appears surprising, because electronics retailers report that although their是指零售商的销售 overall sales were considerably lower than in the previous year, their sales revenue from Denoma models actually grew, largely thanks to some innovative and popular models that Denoma introduced.
D的销售收入下降
零售商总体销售下降，来自于D的销售收入增加，因为D引进了新的受欢迎的Models
Which of the following, if true, does most to explain the apparently surprising result?

A.        Because of the need to educate the public about its new models’ capabilities, Denoma’s advertising spending was higher than normal over the period.（讨论的是收入，与利润成本无关）
B.        For the period at issue, Denoma’s major competitors reported declines in revenue that were, in percentage terms, greater than Denoma’s.
C.        A significant proportion of Denoma’s revenue comes from making components for other consumer-electronics manufacturers. D公司销给零售商部分增加，而这部分对D公司是很少部分，故其总销售额还是降，而零售商销D公司部分销售额增加，而整体部分还是减少。从而解释了原文这状况。另外，从零售商总体销售下降可以得出其他生产者销售收入不佳，也就部分说明了D除了销给零售商所得的那部分收入以外的收入是下降的。
D.        Unlike some of its major competitors, Denoma has no lines of business outside consumer electronics to provide revenue when retail sales of consumer electronics are weak.（反证）
E.        During the period, consumer-electronics retailers sold remaining units of Denoma’s superseded models at prices that were deeply discounted from those models’ original prices. 。E只能解释零售商利润增加，不能解释D公司和零售商销售额下降。
原文要解释的是：D公司销售额大幅度下降。零售商总的销售额大幅度下降，而D公司产品的销售额却由于D公司的新产品而实际增加。正确选项要和这情况相符合C说明整体销售额是下降的（零售商和D公司）

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T-4-Q28
In Berinia, the age at which people could begin to drink alcohol legally used to be 18. In 1990, in an attempt to reduce alcohol consumption and thereby to reduce alcohol-related traffic deaths among Berinians under 21, the legal drinking age was raised to 21. Alcohol-related traffic deaths among people under 21 have decreased significantly since 1990. nevertheless, surveys show that people in that age-group drink just as much alcohol as they did before 1990.u
法定喝酒年龄18---21
目的：减少21岁以下  喝酒consumption + 酒后驾车事故
结果：酒后驾车事故减少了，但是21岁以下的人喝酒数量没有减少
Which of the following, if true of Berinia, most help to resolve the apparent discrepancy?
A.        For the population as a whole, annual alcohol consumption is no lower now than it was in 1990
B.        Alcohol consumption away from home, for example in bars and restaurants, is much lower among people under 21 than it was in 1990意思就是在家里面喝酒就不出去开车了。
C.        The proportion of people under 21 who own a car is higher now than it was in 1990
D.        Alcohol consumption is lower among people under 21 than among adults in most other age-groups.
E.        Alcohol-related traffic deaths among people over 21 have increased slightly since 1990.
文章没有在说比率，Alcohol-related traffic deaths among people under 21 have decreased significantly since 1990，是说绝对值哦
The problem with C is that:
X = total number of people under 21 in Berinia
Y% = total percent of people who drinks (remains relatively constant)
A% = total percent of car owners under the 21 BEFORE the change in legal drinking age
B% = total percent of car owners under the 21 AFTER the change

The amount of people who can drink and drive before: X * Y * A
The amount of people who can drink and drive after: X * Y * B
Based on the condition that B > A we can conclude that after > before, doesn't explain the decrease in alcohol-related traffic death.
I always figure out the constant factors first, stop paying attention to them and then focus on what's changed.  Without listing out the formulas, you can figure out that X and Y remained constant.  So focus on the only thing that changed (car owners) and see how it affects the overall result (accidents).