2016年托福阅读复习模拟练习及答案解析一

　　托福阅读原文

　　Research has shown that certain mineralsare required by plants for normal growth and development. The soil is thesource of these minerals, which are absorbed by the plant with the water fromthe soil. Even nitrogen, which is a gas in its elemental state, is normallyabsorbed from the soil as nitrate ions. Some soils are notoriously deficient inmicro nutrients and are therefore unable to support most plant life. So-calledserpentine soils, for example, are deficient in calcium, and only plants ableto tolerate low levels of this mineral can survive. In modern agriculture,mineral depletion of soils is a major concern, since harvesting cropsinterrupts the recycling of nutrients back to the soil.

　　Mineral deficiencies can often be detectedby specific symptoms such as chlorosis (loss of chlorophyll resulting in yellowor white leaf tissue), necrosis (isolated dead patches), anthocyanin formation(development of deep red pigmentation of leaves or stem), stunted growth, anddevelopment of woody tissue in an herbaceous plant. Soils are most commonlydeficient in nitrogen and phosphorus. Nitrogen-deficient plants exhibit many ofthe symptoms just described. Leaves develop chlorosis; stems are short andslender, and anthocyanin discoloration occurs on stems, petioles, and lowerleaf surfaces. Phosphorus-deficient plants are often stunted, with leavesturning a characteristic dark green, often with the accumulation ofanthocyanin. Typically, older leaves are affected first as the phosphorus ismobilized to young growing tissue. Iron deficiency is characterized bychlorosis between veins in young leaves.

　　Much of the research on nutrientdeficiencies is based on growing plants hydroponically, that is, in soillessliquid nutrient solutions. This technique allows researchers to createsolutions that selectively omit certain nutrients and then observe theresulting effects on the plants. Hydroponics has applications beyond basicresearch, since it facilitates the growing of greenhouse vegetables duringwinter. Aeroponics, a technique in which plants are suspended and the rootsmisted with a nutrient solution, is another method for growing plants withoutsoil.

　　While mineral deficiencies can limit thegrowth of plants, an overabundance of certain minerals can be toxic and canalso limit growth. Saline soils, which have high concentrations of sodiumchloride and other salts, limit plant growth, and research continues to focuson developing salt-tolerant varieties of agricultural crops. Research hasfocused on the toxic effects of heavy metals such as lead, cadmium, mercury,and aluminum; however, even copper and zinc, which are essential elements, canbecome toxic in high concentrations. Although most plants cannot survive inthese soils, certain plants have the ability to tolerate high levels of theseminerals.

　　Scientists have known for some time thatcertain plants, called hyper accumulators, can concentrate minerals at levels ahundredfold or greater than normal. A survey of known hyper accumulatorsidentified that 75 percent of them amassed nickel, cobalt, copper, zinc,manganese, lead, and cadmium are other minerals of choice. Hyper accumulatorsrun the entire range of the plant world. They may be herbs, shrubs, or trees.Many members of the mustard family, spurge family, legume family,and grass family are top hyper accumulators. Many are found in tropical andsubtropical areas of the world, where accumulation of high concentrations ofmetals may afford some protection against plant-eating insects and microbial pathogens.

　　Only recently have investigators consideredusing these plants to clean up soil and waste sites that have been contaminatedby toxic levels of heavy metals–an environmentally friendly approach known asphytoremediation. This scenario begins with the planting of hyper accumulatingspecies in the target area, such as an abandoned mine or an irrigation pondcontaminated by runoff. Toxic minerals would first be absorbed by roots butlater relocated to the stem and leaves. A harvest of the shoots would removethe toxic compounds off site to be burned or composted to recover the metal forindustrial uses. After several years of cultivation and harvest, the site wouldbe restored at a cost much lower than the price of excavation and reburial, thestandard practice for remediation of contaminated soils. For examples, in fieldtrials, the plant alpine pennycress removed zinc and cadmium from soils near azinc smelter, and Indian mustard, native to Pakistan and India, has beeneffective in reducing levels of selenium salts by 50 percent in contaminatedsoils.

　　托福阅读试题

　　1. According to paragraph 1, what is trueof plants that can grow in serpentine soil?

　　A.They absorb micronutrients unusuallywell.

　　B.They require far less calcium than mostplants do.

　　C.They are able to absorb nitrogen in itselemental state.

　　D.They are typically crops raised for food.

　　2. The word “exhibit”in the passage(paragraph 2) is closest in meaning to

　　A. fight off

　　B. show

　　C.cause

　　D.spread

　　3. According to paragraph 2, which of thefollowing symptoms occurs in phosphorus-deficient plants but not in plantsdeficient in nitrogen or iron?

　　A.Chlorosis on leaves

　　B.Change in leaf pigmentation to a darkshade of green

　　C.Short, stunted appearance of stems

　　D.Reddish pigmentation on the leaves orstem

　　4. According to paragraph 2, a symptom ofiron deficiency is thepresence in young leaves of

　　A.deep red discoloration between the veins

　　B.white or yellow tissue between the veins

　　C.dead spots between the veins

　　D.characteristic dark green veins

　　5. The word “facilitates”in the passage(paragraph 3) is closest in meaning to

　　A.slows down

　　B. affects

　　C. makes easier

　　D. focuses on

　　6. According to paragraph 3, what is theadvantage of hydroponics forresearch on nutrient deficiencies in plants?

　　A.It allows researchers to control whatnutrients a plant receives.

　　B.It allows researchers to observe thegrowth of a large number of plants simultaneously.

　　C.It is possible to directly observe theroots of plants.

　　D.It is unnecessary to keep misting plantswith nutrient solutions.

　　7. The word “suspended”in the passage(paragraph 3) is closest in meaning to

　　A.grown

　　B.protected

　　C.spread out

　　D.hung

　　8. Why does the author mention “herbs”, “shrubs”,and “trees”? (paragraph 5)

　　A.To provide examples of plant types thatcannot tolerate high levels of harmful minerals.

　　B.To show why so many plants are hyperaccumulators.

　　C.To help explain why hyper accumulatorscan be found in so many different places.

　　D.To emphasize that hyper accumulatorsoccur in a wide range of plant types.

　　9. The word “afford”in the passage(paragraph 5) is closest in meaning to

　　A.offer

　　B.prevent

　　C.increase

　　D.remove

　　10. Which of the sentences below bestexpresses the essential information in the highlighted sentence in the passage(paragraph 6)? Incorrect choices change the meaning in important ways or leaveout essential information.

　　A.Before considering phytoremediation, hyperaccumulating species of plants local to the target area must be identified.

　　B.The investigation begins with anevaluation of toxic sites in the target area to determine the extent ofcontamination.

　　C.The first step in phytoremediation is theplanting of hyper accumulating plants in the area to be cleaned up.

　　D.Mines and irrigation ponds can be keptfrom becoming contaminated by planting hyper accumulating species in targetedareas.

　　11. It can be inferred from paragraph6 thatcompared with standard practices for remediation of contaminated soils,phytoremediation

　　A.does not allow for the use of the removedminerals for industrial purposes

　　B.can be faster to implement

　　C.is equally friendly to the environment

　　D.is less suitable for soils that need tobe used within a short period of time

　　12. Why does the author mention “Indianmustard”? (paragraph 6)

　　A.To warn about possible risks involved inphytoremediation

　　B.To help illustrate the potential of phytoremediation

　　C.To show that hyper accumulating plantsgrow in many regions of the world

　　D.To explain how zinc contamination can bereduced

　　13. Look at the four squares [■]that indicate where the following sentence could be added to the passage. Certainminerals are more likely to be accumulated in large quantities than others.

　　Scientists have known for some time thatcertain plants, called hyper accumulators, can concentrate minerals at levels ahundredfold or greater than normal. ■ 【A】A survey ofknown hyper accumulators identified that 75 percent of them amassed nickel,cobalt, copper, zinc, manganese, lead, and cadmium are other minerals ofchoice. ■ 【B】Hyper accumulators run the entire range of the plant world. ■ 【C】They may beherbs, shrubs, or trees. ■ 【D】Many members of the mustard family, spurge family, legumefamily, and grass family are top hyper accumulators. Many are found in tropicaland subtropical areas of the world, where accumulation of high concentrationsof metals may afford some protection against plant-eating insects and microbialpathogens.

　　Where could the sentence best fit?

　　14. Directions: An introductory sentencefor a brief summary of the passage is provided below. Complete the summary byselecting the THREE answer choices that express the most important ideas in thepassage. Some answer choices do not belong in the summary because they expressideas that are not presented in the passage or are minor ideas in the passage.This question is worth 2 points.

　　Plants need to absorb certain minerals fromthe soil in adequate quantities for normal growth and development.

　　A.Some plants are able to accumulateextremely high levels of certain minerals and thus can be used to clean upsoils contaminated with toxic levels of these minerals.

　　B.Though beneficial in lower levels, highlevels of salts, other minerals, and heavy metals can be harmful to plants.

　　C.When plants do not absorb sufficientamounts of essential minerals, characteristic abnormalities result.

　　D.Because high concentrations of sodiumchloride and other salts limit growth in most plants, much research has beendone in an effort to develop salt-tolerant agricultural crops.

　　E.Some plants can tolerate comparativelylow levels of certain minerals, but such plants are of little use for recyclingnutrients back into depleted soils.

　　F.Mineral deficiencies in many plants canbe cured by misting their roots with a nutrient solution or by transferring theplants to a soilless nutrient solution.

　　托福阅读答案

　　1. 以serpentine soil做关键词定位至倒数第二句，这种土壤钙质缺乏，只有对钙要求很低的植物可以生存。问题问什么样的植物能够生存，所以B正确。A中micronutrients没说，C的nitrogen和elemental state与问题无关，错;D的food没说

　　2. exhibit显示，显出，所以B的show正确。原句说氮缺乏的植物怎么样很多现象，所以是显示很多现象，MS引起很多现象也对，但不一定能把氮缺乏和那些现象联系起来，所以因果关系有些牵强，剩下的A斗争D蔓延完全不对

　　3.以phosphorus-deficientplants做关键词定位至倒数第二句，说phosphorus-deficient，磷缺乏的植物是容易倒的，并且叶子会变成暗绿色，B是答案。A中的chlorosis萎黄病，变色病没说;C中的茎很短原文没说;D中的reddish pigmentation原文没说

　　4.以iron deficiency和young leaves做关键词定位至最后一句，chlorosis变色病，萎黄病，所以B项的white oryellow tissue刚好对上。A项的deep red没说，错;C的dead spots原文没说，错;D的dark green是缺乏磷的症状，不对

　　5. facilitate促进，帮助，使变容易，所以C的makes easier正确。原句说hydroponic除了基本研究之外还有其他应用，就是实际上的应用，说怎么样了冬天里温室蔬菜的生长。从感情色彩上看，这个地方要的是一个正向词，A的slow down和B的affect都不对。只是focus on还不行，必须正向，所以答案是make easier

　　6.以nutrient deficiency做关键词定位至第一句，但第一句只是给这个无土栽培下了个定义，第二句才开始说好处，使得researchers能够有意去掉某种营养，然后看效果，也就是A说的可以选择让植物吸收什么营养;其他三项都完全没说

　　7. suspend悬垂，悬挂，所以hung是正确答案。原句中acroponics意思是空气种植法，acro表示悬空，所以后面的解释是把植物怎么样，而且跟后面的mist并列，mist混合。混合与成长是不能并列的，grow错;同样spring长出来也不对;protect是完全不靠谱的

　　8.修辞目的题，而且这句话中有个they，指代前文，所以往前看，说HA在整个植物界分布广泛，后面的几种植物就是HA的例子，所以答案是D。A说cannot tolerate反了;原文没说到原因，所以B/C都错

　　9. afford买得起，能承受，所以offer提供，给出是正确答案。很多物种都生长在热带及亚热带地区，那儿的高浓度金属可以怎么样保护植物免遭吃植物的昆虫的捕食。B的prevent防止保护和D的remove去除保护肯定不对;increase增加保护是在原有的基础上增加，原文没说原来就有保护，所以increase不对

　　10.原句的结构是这件事开始于blabla在某地，比如blabla地区;A中的before是没说的，原文一直在说这件事开始于什么什么，这件事之前干嘛没说;原文有个很难替换的词HAS，而这个词在B答案中没有，所以B 错;C同义替换，正确;D把such as里面的例子变成了句子的主要部分，改变了结构，错

　　11.以contaminated soil和remediation做关键词定位至倒数第二句，说经过若干年的耕种与收割之后，那个地方就会恢复，说明没有若干年就不能恢复，所以D正确。A/C没有相关信息;B说反，应该是传统的挖掘方法更快，新的种植物的方法慢

　　12.修辞目的题，Indian mustard做关键词定位至最后一句，这句话整个是个例子，而且之前的那句话也是个例子。再往前就是上题的那句话，也就是说经过若干年耕种与收割，那个地方就会变好，也就是这种方法有用，所以答案B正确

　　13.三个过渡点，certainminerals，large quantities和代词others，有mineral的只有A和B两个选项;带入之后发现A是正确的，待插入句说有的矿物比别的矿物更容易沉积，而原文的第二句是对待插入句的一种解释，所以应该放在待插入句之后，所以A对B错

　　14. some plants are选项对应原文第五段和第六段的第一句，正确

　　though选项对应原文第四段第一句，正确

　　when选项对应原文第二段第一句，正确

　　because选项中的因果关系原文没说，而且氯化钠也是个细节，不选

　　some plants can选项是第一段的一个细节，不选

　　mineral deficiency选项是原文第三段的一个细节，不选