北京接连发布红色预警，让小编心里也是怕怕的。然而，雾霾背后其实有着丰富的GMAT逻辑分析文本，此话怎样？且看新东方GMAT教师张鹏老师用GMAT逻辑帮你分析双号车才是导致雾霾的罪魁祸首。
PM2.5破千已经很雷了，再限个单双号更是雷上加雷，如果还能给GMAT贡献素材，只能是雷布斯了。
杀鸡中，别闹，请听题：
文风略陡壁，我们假装严肃地整理成官方题目的模样：
“昨天全部单号车被限行，但是PM2.5浓度与前天相同，所以双号车才是导致雾霾的原因。”
请问作者在推理的过程中，做了什么假设?
现在请和我一起开启学霸模式，采用GMAT职业病的思路层层剖析，并佐以GMAT真题来映衬大家求知若渴的表情。
第一弹
对比实验乃永恒的考点，必须设置单一变量观察实验结果。不然在GMAT范围，我们就聊不下去了。
题目下了好大一盘棋，居然拿全体单号车当作变量，you must be逗我……
强化班课堂再现：文章只针对现象提出原因的，正确选项一般直接设计对比实验;文章如果已经设计好对比实验，正确选项一般其它干扰变量。(忘了的同学还不快翻翻讲义)
所以，任何可以导致雾霾或者消除雾霾的原因，如果在昨天与前天有所不同，都可以是干扰变量。参考答案方向：
1. 昨天各类工厂不能排放比前天更多的PM2.5颗粒。
2. 昨天的风不能比前天更小。
说好的GMAT例题……想想还是算了。为了不影响这篇美文的节奏，我们把题放到最后。作为学霸的你，一定会猛搓大拇指刷到最后的最后，放学憋走……
第二弹
上一弹的问题默认为解决啦，那么对比实验的最后结论是：单号车不是导致雾霾的原因。
强化班课堂再现：无因无果视为加强，此乃验证一组因果关系;无因有果视为削弱，此乃破坏一组因果关系。但，只是一组哦，管不了别的组。
所以，“单号车不是导致雾霾的原因”，并不代表“双号车是导致雾霾的原因”，除非：
车是导致雾霾的原因。(不必假设车是唯一原因，思考题。)
这是作者逻辑最大的硬伤，简言之，跟车杠上了。无车不欢，非此即彼，二元论控，把错综复杂的人生概括为简明扼要的零和博弈。你的东隅一定是我的桑榆，老子跟你拼了。
此处应有一个题，继续往下洗刷刷，放学依旧憋走……
第三弹
这是考频不高的思路，但一出现仍然动若脱兔，令你难以自持，我直说了。
雾霾消除的弛豫时间不能太长。请说人话：拿走一个导致雾霾的原因，必须立竿见影。
否则，单号车搞出一堆雾霾，绕梁三日浓得散不掉;只见它一个华丽转身，库里般第三节打卡下班，留下双号车独守空街。但雾霾当然还是那个雾霾，好意思拿无因有果给自己洗白吗?
若这一段没想明白，请务必放学憋走，一口气刷到最后……
不过，差不多真放学了。希望这三个GMAT高频考点，时时萦绕在你脑中，久久不能忘怀，也不枉我陡壁一场。
想听真人秀，寒假听个够：约！
新东方GMAT教师 张鹏
最后紧急插播3道GMAT题目，全是assumption题：
第一弹
The milk of many mammals contains cannabinoids, substances that are known to stimulate certain receptors in the brain. To investigate the function of cannabinoids, researchers injected newborn mice with a chemical that is known to block cannabinoids from reaching their receptors in the brain. The injected mice showed far less interest in feeding than normal newborn mice do. Therefore, cannabinoids probably function to stimulate the appetite.
Which of the following is an assumption on which the argument depends?
A. Newborn mice do not normally ingest any substance other than their mothers’ milk.
B. Cannabinoids are the only substances in mammals’ milk that stimulate the appetite.
C. The mothers of newborn mice do not normally make any effort to encourage their babies to feed.
D. The milk of mammals would be less nutritious if it did not contain cannabinoids.
E. The chemical that blocks cannabinoids from stimulating their brain receptors does not independently inhibit the appetite.
避免剧透，答案在后。
第二弹
In 1992 outlaw fishing boats began illegally harvesting lobsters from the territorial waters of the country of Belukia. Soon after, the annual tonnage of lobster legally harvested in Belukian waters began declining; in 1996, despite there being no reduction in the level of legal lobster fishing activity, the local catch was 9,000 tons below pre-1992 levels. It is therefore highly likely that the outlaw fishing boats harvested about 9,000 tons of lobster illegally that year.
Which of the following is an assumption on which the argument depends?
A. The illegal lobster harvesting was not so extensive that the population of catchable lobsters in Belukia’s territorial waters had sharply declined by 1996.
B. The average annual lobster catch, in tons, of an outlaw fishing boat is has increased steadily since 1992.
C. Outlaw fishing boats do not, as a group, harvest more lobsters than do licensed lobster-fishing boats.
D. The annual legal lobster harvest in Belukia in 1996 was not significantly less than 9,000 tons.
E. A significant proportion of Belukia’s operators of licensed lobster-fishing boats were out of business between 1992 and 1996.
第三弹
Because ethylene dibromide, a chemical used to fumigate grain, was blamed for the high rate of nerve damage suffered by people who work in grain-processing plants, many such plants switched to other chemical fumigants two years ago. Since then, however, the percentage of workers at these plants who were newly diagnosed with nerve damage has not dropped significantly. Therefore, either ethylene dibromide was wrongly blamed or else the new chemicals also cause nerve damage.
Which of the following is an assumption on which the argument depends?
A. If the new chemicals cause nerve damage, the nerve damage caused would be different from any nerve damage that ethylene dibromide may cause.
B. There are no chemical fumigants that are completely safe for workers in grain-processing plants.
C. If ethylene dibromide causes nerve damage, it does not take two years or longer for that damage to become detectable.
D. Workers at grain-processing plants typically continue to work there even after being diagnosed with nerve damage.
E. Workers at grain-processing plants that still use ethylene dibromide continue to have a high rate of nerve damage.
快速讲解站：
第一弹
对比变量为cannabinoids，干扰变量为注射的chemical，选E.
第二弹
合法船少捞9000吨，不代表非法船多捞9000吨，要假设总量不变，选A.
第三弹
如果ethylene dibromide的破坏效果持续2年，那么现在还为时尚早，选C.
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