10.5 考研英语阅读题源外刊模拟试题【难度5.8&6.5】

Section II Reading Comprehension 

Part A 

Directions: Read the following four texts. Answer the questions below each text by choosing A, B, C or D. Mark your answers on the ANSWER SHEET. 

Text 3

Few smells are as evocative as the earthy scent that rises when rain falls after a long dry spell. Known as petrichor, it seems to stir the brain's centres of memory and emotion, perhaps for reasons rooted in human evolution. But as climate change reshapes weather and landscapes, petrichor is likely to change too.

The scent begins in the soil. During dry periods, soil bacteria produce a compound called geosmin, which keeps insects such as fruit flies away: to them it signals that the plant matter the bacteria are growing on is unappetising and possibly toxic. Humans, for their part, can detect geosmin at astonishingly low concentrations.

Plants contribute as well. In a drought they release aromatic oils that help protect them from intense heat and limit water loss. When raindrops strike parched ground, they trap tiny bubbles of air filled with geosmin and these oils; the bubbles rise, burst and scatter fine particles that drift into our noses.

How petrichor changes will vary from place to place and year to year, but the broad pattern is that regions receiving more rain will have less of it, while regions suffering drought will have more. Drought lets geosmin accumulate, and higher temperatures make the bacteria produce still more by speeding up the chemical reactions inside them, so when rain finally arrives, more of the compound is released. Yet if soil becomes too dry, the geosmin dries out too and is never released.

Where rain falls often, there will be less petrichor, because the compounds lack time to build up between showers. Heavy downpours, which are growing more common as the planet warms, are also too forceful to trap the tiny bubbles that launch the scent; instead the compounds are diluted, driven underground or swept into floodwater. Degraded soil, itself made worse by heat and heavy rain, supports fewer geosmin-producing bacteria as well.

The consequences will not end with what humans smell. Insects that respond to petrichor will have to adjust their behaviour. In places where it is plentiful, mosquitoes are likely to become more numerous, since the scent tells them that dry ground has turned into moist, fertile terrain for laying eggs.

31. According to Paragraphs 2 and 3, the scent of petrichor reaches the air when
A. raindrops trap bubbles of geosmin and oils that then burst
B. soil bacteria start producing geosmin once the rain begins
C. plants discharge geosmin directly to protect themselves from heat
D. insects disturb the soil and stir geosmin into the air

32. According to Paragraph 4, hotter temperatures during a drought lead to more geosmin because heat
A. forces plants to release more protective oils
B. lets the compound travel further through the air
C. speeds up the chemical reactions inside the bacteria
D. makes the bacteria multiply more quickly

33. Which of the following situations would most likely produce the strongest petrichor?
A. Light showers falling every few days throughout the year.
B. A violent storm that floods soil already soaked for weeks.
C. Soil so parched that its geosmin has dried up completely.
D. A hot dry spell finally broken by the first rain in months.

34. The author mentions fruit flies in Paragraph 2 and mosquitoes in the last paragraph to show that insects
A. read the scent as a clue to their surroundings
B. are driven away by every strong natural smell
C. help to carry geosmin over long distances
D. rely on geosmin to locate their main food source

35. Which of the following best summarises the text?
A. Petrichor will gradually fade everywhere as the climate warms.
B. Climate change will alter petrichor unevenly across regions, with effects beyond human smell.
C. Humans' acute sensitivity to geosmin evolved to help them find water.
D. The chemistry of petrichor is too poorly understood for any change to be predicted.

附注：根据历年考研英语真题阅读题源外刊等，摘选最新文章，模拟仿真出题。

参考答案见以下。

Quick look: ACDAB

31.【正确答案】A
【解析】题型：细节理解题（过程辨析）
定位：第二段 "During dry periods, soil bacteria produce a compound called geosmin..." 与第三段 "When raindrops strike parched ground, they trap tiny bubbles of air filled with geosmin and these oils; the bubbles rise, burst and scatter fine particles..."
分析：气味的形成分两步。干旱期间，土壤细菌先产生土臭素，植物释放芳香油。降雨时，雨滴打在干燥地面上，裹进含土臭素和芳香油的微小气泡，气泡升起破裂，细小颗粒散入空气，人才闻到。A项对应这一过程。
干扰项：[B]"雨一开始细菌才开始产生土臭素"颠倒时序，原文明确土臭素是在干旱期间产生的，降雨只是把它释放出来；[C]"植物直接释放土臭素"张冠李戴，土臭素由细菌产生，植物释放的是芳香油；[D]"昆虫扰动土壤、把土臭素搅入空气"无中生有，原文中昆虫只是对气味作出反应，并不参与气味的散发。

32.【正确答案】C
【解析】题型：细节理解题（因果）
定位：第四段 "higher temperatures make the bacteria produce still more by speeding up the chemical reactions inside them"
分析：干旱使土臭素不断累积，升温则进一步加快细菌体内的化学反应，使其产量更高，所以降雨来临时释放的土臭素更多。C项直接对应。
干扰项：[A]"迫使植物释放更多保护性油脂"偷换概念，芳香油是植物对干旱高温的防护反应，与"土臭素增多"是两回事，原文也没有把升温与油脂增多挂钩；[B]"使化合物传播得更远"无中生有，原文没有讨论气味的传播距离；[D]"使细菌繁殖更快"偷换概念，原文说的是加快每个细菌体内的反应、提高产量，并非细菌数量增加，而且第五段还提到高温与暴雨造成的土壤退化会使细菌变少。

33.【正确答案】D
【解析】题型：推理判断题（综合应用）
定位：第四段 "Drought lets geosmin accumulate... when rain finally arrives, more of the compound is released. Yet if soil becomes too dry..."；第五段 "Where rain falls often... Heavy downpours... too forceful..."
分析：本题要整合第四、五段。干旱加高温使土臭素不断累积、产量上升，久旱后的第一场雨释放得最多，所以最可能产生最强的气味。D项符合。其余三项分别对应原文明确指出会削弱气味的情形。
干扰项：[A]"每隔几天一场小雨"对应第五段"降雨频繁，化合物来不及积累，气味更弱"；[B]"猛烈暴雨淹没浸泡数周的土壤"对应第五段"暴雨过于猛烈，无法形成气泡，化合物被稀释、冲入地下或混入洪水"；[C]"干到土臭素已经耗尽的土壤"对应第四段末句"过于干燥时土臭素会干掉而无法释放"，这是"越旱气味越强"这一直线思维的陷阱。

34.【正确答案】A
【解析】题型：例证/功能推理题（跨段）
定位：第二段 "keeps insects such as fruit flies away: to them it signals that the plant matter... is unappetising and possibly toxic" 与末段 "the scent tells them that dry ground has turned into moist, fertile terrain for laying eggs"
分析：两个例子的反应截然相反，果蝇被驱离，蚊子被吸引。共同点是，昆虫都把气味当作周围环境的信息，一个判断食物能不能吃，一个判断地面适不适合产卵。A项抓住这一共性。
干扰项：[B]"被每一种强烈的自然气味驱离"以偏概全，蚊子的例子恰恰是被吸引；[C]"帮助土臭素远距离传播"无中生有，两个例子都只涉及昆虫对气味的反应，没有涉及传播；[D]"依靠土臭素寻找主要食物"无中生有，果蝇是被土臭素驱离，蚊子借气味判断的是产卵环境，而不是食物。

35.【正确答案】B
【解析】题型：主旨大意题
定位：第四段首句 "How petrichor changes will vary from place to place and year to year..." 与末段首句 "The consequences will not end with what humans smell."
分析：全文先交代气味的成因，再说明气候变化的影响因地而异（多雨处减弱，干旱处增强，过干又不行），最后延伸到昆虫行为。B项同时概括了"因地而异"与"影响超出人类嗅觉"两条主线。
干扰项：[A]"各地都将逐渐减弱"以偏概全，与第四段"干旱地区将增多"相反；[C]"人类对土臭素敏感是为了找水"无中生有，首段只说气味引发的情感反应"或许与进化有关"，并未提到找水；[D]"化学机制了解太少，无法预测变化"与原文相反，全文给出的是具体而有条件的预测。

【参考译文】

在漫长的干旱期过后，雨水降落时空气中弥漫的那种独特的泥土气息，往往能勾起人们浓浓的怀旧之情。这种被称为“雨后泥土芬芳”（petrichor）的气味，能直接触动大脑中负责记忆与情感的区域——这其中的缘由或许与人类的进化历程息息相关。然而，随着气候变化改变地球的天气与环境，这种芬芳的气息也将随之发生变化。

首先，了解这种气味产生的原因很有必要。在干旱时期，土壤中的细菌会产生一种名为“土臭素”（geosmin）的化合物，以此来驱赶果蝇等昆虫。这种化学物质向果蝇发出信号，表明细菌赖以生存的植物物质既不可口，甚至可能含有毒性。与此同时，土臭素也能吸引跳虫等有助于传播孢子的动物，从而促进该化合物的进一步扩散。

“人类对土臭素极其敏感，”瑞典卡罗林斯卡医学院（Karolinska Institute）专门研究嗅觉感知的心理学家约翰·伦德斯特伦（Johan Lundström）说道，“即便是在一个奥林匹克标准泳池的水量中混入一滴土臭素，我们依然能闻到它的气味。”

除了土壤细菌产生土臭素外，植物在干旱期间也会释放芳香油，形成一道保护层，以抵御酷热并减少水分流失。当雨滴落在干燥的地面和植物上时，撞击产生的微小气泡会裹挟着土臭素和芳香油升入空中；随后气泡破裂，散发出微小的颗粒，进而进入人类的鼻腔。

这种“雨后泥土芬芳”具体会发生怎样的变化，取决于你身处何地，因为全球气温升高对天气和气候模式的影响因地区和年份而异。丹麦奥尔堡大学（Aalborg University）微生物生理学教授杰佩·伦德·尼尔森（Jeppe Lund Nielsen）指出，总体而言，降雨量增加的地区，这种气味出现的频率会降低；而在遭遇干旱的地区，这种气味则会更频繁地出现。

干旱会导致土臭素积聚；若干旱伴随着高温，细菌产生的土臭素量会进一步增加，因为高温加速了微生物体内的化学反应。“气温越高，这些化合物的产量也就越高，”尼尔森说道。因此，当最终降雨来临时，释放出的土臭素量也会更多。但如果土壤过于干燥，“土臭素就会干结而无法释放，”伦德斯特伦（Lundström）说道。

在降雨频繁的地区，雨后泥土气息（petrichor）会相对较弱，因为芳香化合物没有足够的时间积累。此外，随着全球变暖而日益频繁的强降雨，其冲击力过大，无法像细雨那样裹挟微小气泡将气味带入空气中；相反，这些化合物会被稀释、冲入地下或混入地表径流中。

土壤退化——这也是气温升高和强降雨增多带来的后果——同样起着作用，因为这意味着能产生土臭素的细菌数量会减少。

土臭素的变化带来的影响远不止人类嗅觉层面的改变。尼尔森（Nielsen）指出，那些会对雨后泥土气息产生反应的昆虫也不得不调整其行为。例如，雨后泥土气息浓郁的地区蚊子数量可能会增加，因为这种气味向昆虫传递了一个信号：原本干燥的地面已转变为湿润肥沃的环境，适宜产卵。

附注：