On viewing thelushplant growth of atropicalrain forest, most people wouldconcludethat the soilbeneathit is rich in nutrients. However, although rain forest soils are highlyvariable, they have incommonthe fact thatabundantrainfallwashesmineralnutrients out of them and into streams. Thisprocessis known as leaching. Because of rain leaching, mosttropicalrain forest soils have low to very lowmineralnutrientcontent, indramaticcontrastto mineral-rich grassland soils. Tropicalforest soils also oftencontainparticulartypes of clays that, unlike the mineral-binding clays oftemperateforest soils, do notbindmineralions well. Aluminumis thedominantcation (positively chargedion) present intropicalsoils; but plants do notrequirethiselement, and it is moderatelytoxicto a wide range of plants. Aluminumalso reduces theavailabilityofphosphorus, anelementin high demand by plants.

Highmoistureand temperatures speed the growth of soil microbes thatdecomposeorganiccompounds, sotropicalsoils typicallycontainfarloweramounts oforganicmaterials (humus) than do other forest or grassland soils. Becauseorganiccompounds help loosencompactclaysoils, hold water, andbindmineralnutrients, therelativelackoforganicmaterials intropicalsoils is deleterious to plants. Plant roots cannotpenetratefar into hardclaysoils, and during dry periods, the soil cannot hold enough water tosupplyplant needs. Because theconcentrationof dark-coloredorganicmaterials is low intropicalsoils, they are often colored red or yellow by the presence of iron, aluminum: and manganese oxides; when dry, these soils become rock hard. The famous Cambodian temples of Angkor Wat, which have survived for many centuries, were constructed from blocks of such hard rain forest soils.

Given such poor soils, how canlushtropicalforests exist? The answer is that the forest's minerals are held in its living biomass—the trees and other plants and the animals. Incontrastto grasslands, where a largeproportionof plant biomass is producedunderground, that oftropicalforests is nearly all aboveground. Dead leaves, branches, and other plant parts, as well as the wastes and bodies of rain forest animals,barelyreach the forest floor before they are rapidlydecayedbyabundantdecomposers—bacterialandfungal. Minerals released bydecayare quickly absorbed bymultitudinousshallow, fine tree feeder roots and stored in plant tissues. Manytropicalrain forest plants (like those in other forests) have mycorrhizal (fungus-root) partners whosedelicatehyphaespreadthrough great volumes of soil, from which theyreleaseandabsorbminerals and ferry them back to thehostplant inexchangefor neededorganiccompounds. Thefungalhyphae are able toabsorbphosphorusthat plant roots could not themselvesobtainfrom the verydilutesoil solutions, andfungalhyphae cantransfermineralnutrients from one forest plant to another. Consequently,tropicalrain forests typically have what are known as closednutrientsystems, in which minerals are handed off from oneorganismto another with little leaking through to the soil. Whenmineralnutrients do not spend much time in the soil, they cannot be leached into streams. Closednutrientsystems have evolved inresponseto the leaching effects of heavytropicalrainfall. Evidencefor this conclusion is thatnutrientsystems are more open in the richesttropicalsoils and tightest in the poorest soils.

The growth of organisms is dependent on theavailabilityof nutrients, none of which is more important thannitrogen. Although there is anabundantsupplyofnitrogenin Earth’satmosphere, it cannot be absorbed by plants unless it is “fixed,” or combined chemically with other elements to formnitrogencompounds. Nitrogen-fixingbacteriahelptropicalrain forest plants cope with the poor soils there by supplying them with needednitrogen. Manyspeciesoftropicalrain forest trees belong to thelegumefamily, which is known for associations of nitrogen-fixingbacteriawithinrootnodules. Also, cycads (a type oftropicalplant that resembles a palm tree) produce special aboveground roots thatharbornitrogen-fixing cyanobacteria. By growing above the ground, the roots areexposedto sunlight, which the cyanobacteriarequirefor growth. Nitrogenfixation by free-livingbacteriaintropicalsoils is alsobeneficial.

Questions:
question_stem: According to paragraph 1, one reason that the relatively high levels of aluminum in rain forest soils present a problem for plants is that aluminum
choices: tag: A
text: reduces the mineral-binding capacity of soils

tag: B
text: is somewhat toxic to plants

tag: C
text: makes too much phosphorus available to plants

tag: D
text: is present as a positively charged ion in tropical rain forest soils
answer_key: B
explanation: 【题目翻译】
根据第1段，雨林土壤中铝含量相对高给植物带来问题是因为铝的一个什么原因？
A 降低土壤的矿物结合能力
B 对植物有些毒性。
C 使植物吸收过多的磷
D 在热带雨林土壤中以带正电荷的离子存在。

【判定题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】定位到 Passage 1：Aluminum is the dominant cation (positively charged ion) present in tropical soils; but plants do not require this element, and it is moderately toxic to a wide range of plants. 

【逻辑分析】铝是存在于热带土壤中的主要阳离子（带正电荷的离子），但是植物不需要这种元素，而且它对很多植物都有中度毒性。因此可以得知铝元素含量过高会使植物中毒。

【选项分析】
选项 A 的意思是会降低土壤的矿物质结合能力。不符，错误
选项 B 的意思是对于植物有毒。符合，正确。
选项 C 的意思是会使得太多的磷元素对植物有用。不符，错误
选项 D 的意思是作为带正电荷的离子存在于热带雨林的土壤中。不符，错误

question_stem: According to paragraph 2, clay soils that contain relatively low amounts of organic materials have all of the following disadvantages for plants EXCEPT
choices: tag: A
text: poor water retention

tag: B
text: poor root penetrability

tag: C
text: few soil microbes

tag: D
text: low levels of mineral nutrients
answer_key: C
explanation: 【题目翻译】
根据第2段，含有相对低量有机材料的粘土对植物具有以下所有缺点，除__外。
A 保水性差
B 根系渗透性差
C 土壤微生物很少
D 低水平的矿物质营养素

【判定题型】根据题干中出现的大写“EXCEPT”/"NOT" 等其他明显表示否定的词，可以判定本题为否定事实信息题，需要找出与原文信息不符的那个答案。

【关键词定位】根据关键词“contain relatively low amounts of organic materials”本题定位到原文 Because organic compounds help loosen compact clay soils, hold water, and bind mineral nutrients, the relative lack of organic materials in tropical soils is deleterious to plants. 

【选项分析】
选项 A 的意思是较差的保持水分能力，符合，正确
选项 B 的意思是较差的根茎渗透能力，符合，正确
选项 C 的意思是更少的土壤微生物，无中生有，错误。
选项 D 的意思是更低的矿物营养物质。符合，正确

question_stem: Paragraph 2 supports the idea that, as compared with rain forest soils, grassland soils
choices: tag: A
text: contain a greater variety of soil microbes

tag: B
text: contain less organic material

tag: C
text: are able to hold more water

tag: D
text: are generally lighter colored
answer_key: C
explanation: 【题目翻译】
第2段支持的观点：与雨林土壤相比，草原土壤_____。
A：含有多种土壤微生物。

B：含有较少的有机物质

C：能够容纳更多的水

D：通常是浅色的。

【判定题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“ rain forest soils, grassland soils”,本题定位到原文：......so tropical soils typically contain far lower amounts of organic materials (humus) than do other forest or grassland soils. Because organic compounds help loosen compact clay soils, hold water, and bind mineral nutrients...... 

【逻辑分析】原句意思是：热带土壤通常含有比其他森林或草原土壤低得多的有机物质（腐殖质）。因为有机化合物有助于疏松致密的粘土，保持水分，并结合矿物养分。因此草原土壤就能容有更多的水分。

【选项分析】
选项 A 的意思是有更多种类的土壤微生物，不符，错误
选项 B 的意思是有更少的有机物，不符，错误
选项 C 的意思是能够持有更多的水，符合，正确
选项 D 的意思是颜色更浅。不符，错误

question_stem: Why does the author mention "Angkor Wat"?
choices: tag: A
text: To show that rain forest soils are essentially the same today as they were many centuries ago

tag: B
text: To make the point that rain forest soils have certain advantages over other types of soils

tag: C
text: To illustrate how colorful rain forest soils can sometimes be

tag: D
text: To emphasize how hard rain forest soils can become
answer_key: D
explanation: 【题目翻译】作者为什么提到“吴哥窟”？
A：表明雨林土壤与几个世纪前基本相同。

B：指出雨林土壤比其他类型的土壤有一定的优势。

C：为了说明有时雨林土壤是多么的五彩缤纷。

D：强调雨林土壤如何变得坚硬

【判定题型】根据题干问法“why …… mention”，题目询问“Angkor Wat”的修辞目的，可以判断本题为修辞目的题。

【关键词定位】：根据关键词“Angkor Wat”,定位到原句为 The famous Cambodian temples of Angkor Wat, which have survived for many centuries, were constructed from blocks of such hard rain forest soils. 

【引用内容分析】著名的 Angkor Wat 庙宇就是用热带雨林的黏土砖头做的，它存在了好几个世纪。定位句前面的句子就是在说热带雨林的土壤是很坚硬的。

【选项分析】
选项 A 的意思是为了表明热带雨林的土壤现在和过去一样重要，不符，错误
选项 B 的意思是热带雨林的土壤比其他种类的土壤有几个优点，不符，错误
选项 C 的意思是为了说明有时候热带雨林的土壤可以如何多彩，不符，错误
选项 D 的意思是为了强调热带雨林的土壤可以变得多么硬。符合，正确

question_stem: Paragraph 2 suggests the idea that compared with grassland soils, tropical rain forest soils have all of the following characteristics EXCEPT
choices: tag: A
text: soil microbes grow more slowly

tag: B
text: contain lower amounts of organic materials

tag: C
text: hold less water

tag: D
text: contain iron, aluminum and manganese oxides
answer_key: A
explanation: 【题目翻译】第2段提出，与草原土壤相比，热带雨林土壤具有以下特征？
A：土壤微生物生长较慢。
B：含有少量的有机物质
C：含水量少
D：含有铁、铝和锰的氧化物。

【判定题型】根据题干中出现的大写“EXCEPT”/"NOT" 等其他明显表示否定的词，可以判定本题为否定事实信息题，需要找出与原文信息不符的那个答案。

【关键词定位】：根据题干关键词“tropical rain forest soils”,可以将出题范围锁定在 Passage 2：so tropical soils typically contain far lower amounts of organic materials (humus) than do other forest or grassland soils.和 Because organic compounds help loosen compact clay soils, hold water, and bind mineral nutrients, the relative lack of organic materials in tropical soils is deleterious to plants. 

【选项分析】
选项 A 的意思是更慢的土壤微生物增长速度。A 选项无中生有，不符，错误
选项 B 的意思是含有更少的有机物。符合，正确
选项 C 的意思是含有更少的水。符合，正确
选项 D 的意思是含有更少的铁、铝和镁氧化物。符合，正确

question_stem: The word "multitudinous" in the passage is closest in meaning to
choices: tag: A
text: a great many

tag: B
text: rapidly increasing

tag: C
text: finely divided

tag: D
text: extremely strong
answer_key: A
explanation: 【题目翻译】与文中单词“multitudinous”意思最相近的是？
选项 A 的意思是很多
选项 B 的意思是迅速增长的
选项 C 的意思是细致区分的
选项 D 的意思是非常强壮的

【判定题型】：题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】：本题定位到原文：Minerals released by decay are quickly absorbed by multitudinous shallow, fine tree feeder roots and stored in plant tissues. 

【词汇解析】：词汇“multitudinous”的意思是“多种多样的”。带入到原句中，原句的意思是腐烂过程释放出来的矿物质很快就被大量的浅的、细的根茎吸收掉并储存在植物组织里了。 

【选项分析】
选项 A 的意思是很多，符合，正确
选项 B 的意思是迅速增长的，不符，错误
选项 C 的意思是细致区分的，不符，错误
选项 D 的意思是非常强壮的。不符，错误

question_stem: The word “Consequently” in the passage is closest in meaning to
choices: tag: A
text: Nevertheless

tag: B
text: However

tag: C
text: As a result

tag: D
text: In addition
answer_key: C
explanation: 【题目翻译】与文中单词“consequently”意思最相近的是？
选项 A 的意思是然而，
选项 B 的意思是然而，
选项 C 的意思是结果是，
选项 D 的意思是另外

【判定题型】：题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】：根据关键词“consequently”,定位到原句 Consequently, tropical rain forests typically have what are known as closed nutrient systems, in which minerals are handed off from one organism to another with little leaking through to the soil.

【词汇解析】：词汇“consequently”的意思是“结果是”,带入到原句中，原句的意思是结果是，热带雨林森林一般拥有闭合的营养系统，在这个系统里矿物质从一个有机体几乎没有遗失地被传输去另一个有机体。

【选项分析】
选项 A 的意思是然而，不符，错误
选项 B 的意思是然而，不符，错误
选项 C 的意思是结果是，符合，正确
选项 D 的意思是另外。不符，错误

question_stem: According to paragraph 3, the main advantage of a closed nutrient system is that such a system
choices: tag: A
text: reduces the risk of minerals being lost through leaching

tag: B
text: ensures that all organisms in the system receive an adequate supply of nutrients

tag: C
text: increases the amount of nutrients that plant roots can absorb from soil solutions

tag: D
text: increases the speed with which nutrients are returned to the soil
answer_key: A
explanation: 【题目翻译】根据第3段，封闭营养系统的主要优点是这种系统____。
A：减少矿物质因浸出而流失的风险。

B：确保系统中的所有有机体获得足够的营养。

C:增加植物根系从土壤溶液中吸收的养分量。

D：提高养分返回土壤的速度。

【判定题型】：题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“the main advantage of a closed nutrient system”,定位到 Passage 3，原句为 Consequently, tropical rain forests typically have what are known as closed nutrient systems, in which minerals are handed off from one organism to another with little leaking through to the soil.

【逻辑分析】此处原文的大意是：结果是，热带雨林森林一般拥有闭合的营养系统，在这个系统里矿物质从一个有机体几乎没有遗失地被传输去另一个有机体。 题干问的是闭合的营养系统的好处是什么。

【选项分析】
选项 A 的意思是会降低矿物质丢失的风险，符合，正确
选项 B 的意思是可以确保所有的有机体都接受到足够的营养供给，不符，错误
选项 C 的意思是增加植物根茎可以从土壤溶液里吸收的营养物质的量，不符，错误
选项 D 的意思是增加营养物质返回土壤的速度。不符，错误

question_stem: The word “abundant” in the passage is closest in meaning to
choices: tag: A
text: valuable

tag: B
text: plentiful

tag: C
text: usable

tag: D
text: obvious
answer_key: B
explanation: 【题目翻译】与文中单词“abundant”意思最相近的是？
选项 A 的意思是有价值的，
选项 B 的意思是足够的，
选项 C 的意思是有用的，
选项 D 的意思是明显的。

【判定题型】题目要求选出与高亮单词意思最接近的选项，故判断本题为词汇题。

【关键词定位】：根据关键词“abundant”,定位到原句 Although there is an abundant supply of nitrogen in Earth’s atmosphere, it cannot be absorbed by plants unless it is “fixed,” or combined chemically with other elements to form nitrogen compounds. 

【词汇解析】：词汇“abundant”的意思是“充足的”,带入到原句中，原句的意思是尽管氮在大气中的供给非常充足，除非它被固着或和其他物质结合成氮化合物，它才能被吸收。

【选项分析】
选项 A 的意思是有价值的，不符，错误
选项 B 的意思是足够的，符合，正确
选项 C 的意思是有用的，不符，错误
选项 D 的意思是明显的。不符，错误

question_stem: According to paragraph 4, why can getting enough nitrogen be a problem for plants?
choices: tag: A
text: Because most of Earth’s nitrogen is located in the atmosphere

tag: B
text: Because plants can use the nitrogen they absorb only if they have previously absorbed certain other elements that are often scarce in poor soils

tag: C
text: Because plants cannot absorb nitrogen that has not been chemically combined with other elements

tag: D
text: Because plants have to compete with bacteria for available nitrogen in the soil
answer_key: C
explanation: 【题目翻译】根据第4段，为什么获得足够的氮对植物来说是个问题？
A：因为地球上的大部分氮都位于大气中。

B：因为植物只有吸收了贫瘠土壤中通常稀有的某些其他元素后才能利用它们吸收的氮。

C：因为植物不能吸收未与其它元素化学结合的氮。

D：因为植物必须与细菌竞争土壤中的有效氮。

【判定题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“ problem”,定位到 Passage4，原句为：Although there is an abundant supply of nitrogen in Earth’s atmosphere, it cannot be absorbed by plants unless it is “fixed,” or combined chemically with other elements to form nitrogen compounds. 

【逻辑分析】定位句的大意是：尽管地球大气层中氮的供应丰富，但是除非它是“固定的”，或者与其他元素化学结合形成氮化合物，否则植物不能吸收它。所以得知植物不能吸收单独的氮元素。

【选项分析】
选项 A 的意思是因为大多数地球的氮位于大气层中。不符，错误
选项 B 的意思是因为植物只有在它们吸收过稀少的元素之后才能吸收氮。不符，错误
选项 C 的意思是植物不能吸收没有结合成氮化合物的元素。符合，正确
选项 D 的意思是植物需要和细菌来竞争可用的土壤里的氮元素。不符，错误

question_stem: Paragraph 4 supports the idea that having aboveground roots benefits cycads in which of the following ways?
choices: tag: A
text: By increasing the growth rate of cycads' roots through exposure to sunlight

tag: B
text: By increasing the supply of usable nitrogen available to cycads

tag: C
text: By reducing the amount of nitrogen cycads require

tag: D
text: By reducing cycads’dependence on nitrogen-fixing bacteria
answer_key: B
explanation: 【题目翻译】第4段支持这样一种观点，即具有地上根对苏铁有以下哪种益处？
A：通过晒太阳提高苏铁根系的生长速度
B：通过增加苏铁可用氮的供应
C：通过减少含氮苏铁的量
D：通过减少苏铁对固氮细菌的依赖

【判定题型】题目问的是文章中的具体细节信息，故根据题目问法可以判断本题为事实信息题。

【关键词定位】：根据关键词“benefit”,定位到 Passage 4，原句为 Also, cycads (a type of tropical plant that resembles a palm tree) produce special aboveground roots that harbor nitrogen-fixing cyanobacteria. By growing above the ground, the roots are exposed to sunlight, which the cyanobacteria require for growth.

【逻辑分析】定位句的意思是：此外，苏铁（一种类似于棕榈树的热带植物）产生特殊的地上根，其中含有固氮蓝细菌。通过在地上生长，根部暴露在阳光下，蓝藻生长需要阳光。所以得知这种根茎可以保护固氮的细菌，因为地上根茎可以接触到阳光，而阳光是固氮细菌成长所需要的东西。地上根使得氮元素增加了。

【选项分析】
选项 A 的意思是通过增加光照而提高苏铁属植物的生长率。不符，错误
选项 B 的意思是通过增加可用的氮元素。符合，正确
选项 C 的意思是通过减少苏铁属植物所需的氮元素量。不符，错误
选项 D 的意思是通过降低苏铁属植物对于氮元素的依赖性。不符，错误