2019年托福考试阅读模拟试题及答案解析(1)

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1、2019 年托福考试阅读模拟试题及答案解析（ 1）托福阅读原文Protection of Plants by Insects【1】Many plants - one or more species of at least68different families - can secrete nectar even whenthey have noblossoms, because they bear extrafloral nectaries (structuresthat producenectar) on stems, leaves, leaf stems, or otherstructur

2、es.These plants usually occur where antsare abundant,most in the tropics but some in temperate areas. Among thoseof northeasternNorth America are various plums, cherries,roses, hawthorns, poplars, and oaks. Like floralnectar,extrafloral nectar consists mainly of water with a highcontent of dissolved

3、 sugars and, in some plants, smallamounts of amino acids. The extrafloral nectaries of someplants areknown to attract ants and other insects, but theevolutionary history of most plants with thesenectaries isunknown. Nevertheless, most ecologists believe that allextrafloral nectaries attractinsects t

4、hat will defend theplant.【2】Ants are portably the most frequent and certainlythe most persistent defenders ofplants. Since the highlyactive worker ants require a great deal of energy, plantsexploit thisneed by providing extrafloral nectar thatsupplies ants with abundant energy. To return thisfavor,

5、antsguard the nectaries, driving away or killing intrudinginsects that might competewith ants for nectar. Many of theseintruders are herbivorous and would eat the leaves oftheplants.【3】Biologists once thought that secretion ofextrafloral nectar has some purely internalphysiologicalfunction, and that

6、 ants provide no benefit whatsoever to theplants that secreteit. This view and the opposing“protectionist ” hypothesis that ants defend plants hadbeendisputed for over a hundred years when, in 1910, askeptical William Morton Wheelercommented on the controversy.He called for proof of the protectionis

7、t view ： thatvisitations ofthe ants confer protection on the plants andthat in the absence of the insects a much greaternumber wouldperish or fail to produce flowers or seeds than when theinsects are present. That we now have an abundance of theproof that was called for was established whenBarbara B

8、entleyreviewed the relevant evidence in 1977, and since then manymoreobservations and experiments have provided still furtherproof that ants benefit plants.【4】One example shows how ants attracted to extrafloralnectaries protect morning gloriesagainst attacking insects.The principal insect enemies of

9、 the North American morninggloryfeed mainly on its flowers or fruits rather than itsleaves. Grasshoppers feeding on flowersindirectly blockpollination and the production of seeds by destroying thecorolla or thestigma, which receives the pollen grains and onwhich the pollen germinates. Without theirc

10、olorful corolla,flowers do not attract pollinators and are not fertilized. Anadult grasshoppercan consume a large corolla, about 2.5inches long, in an hour. Caterpillars and seed beetlesaffectseed production directly. Caterpillars devour the ovaries,where the seeds are produced, and seed beetle larv

11、ae eatseeds as they burrow in developing fruits.【5】Extrafloral nectaries at the base of each sepalattract several kinds of insects, but 96 percent of them areants, several different species of them. When buds are stillsmall, lessthan a quarter of an inch long, the sepalnectaries are already present

12、and producing nectar. Theycontinue to do so as the flower develops and while the fruitmatures. Observations leavelittle doubt that ants protectmorning glory flowers and fruits from the combined enemyforceof grasshoppers, caterpillars, and seed beetles. Bentleycompares the seed production of sixplant

13、s that grew wherethere were no ants with that of seventeen plants that wereoccupied byants. Unprotected plants bore only 45 seeds perplant, but plants occupied by ants bore 211 seeds per plant.Although ants are not big enough to kill or seriously injuregrasshoppers, theydrive them away by nipping at

14、 their feet.Seed beetles are more vulnerable because they aremuch smallerthan grasshoppers. The ants prey on the adult beetles,disturb females astheylay their eggs on developing fruits,and eat many of the eggs they do manage to lay.托福阅读试题1.According to paragraph 1 ，floral nectar andextrafloralnectar

15、 are alike in thatA.they are likely to be produced by the same plants.B.they basically consist of the same chemicalcomponents.C.they attract only insects that will defend the plant.D.they are produced by the same parts of the plant.2.To say that ants are persistent defenders of plantsmeans thatA.the

16、y defend plants against a wide variety of threats.B.they continue to defend plants for as long as theplants are threatened.C.they are successful defenders of plants.D.they are easily observable defenders of plants.3.What can be inferred from paragraph 2 about the antsthat are attracted to theextrafl

17、oral nectaries?A.They do not eat the leaves of the plants that produceextrafloral nectar.B.They live almost entirely on extrafloral nectar.C.They spend most of their energy guarding extrafloralnectaries.D.They frequently fight among themselves overextrafloral nectar.4.According to paragraph 3, what

18、was the position of theopponents of theprotectionist hypothesis?A.Extrafloral nectar provides plants with a directdefense against attack by insects.B.Ants substantially benefit plants that secreteextrafloral nectar.C.The secretion of extrafloral nectar plays a role inthe plant s internal functioning

19、.D.Ants visit plants that secrete extrafloral nectar asoften as they visit plants that do not.5.The word skeptical in the passage is closest inmeaning toA.curious.B.doubtful.C.open-minded.D.practical.6.Which of the sentences below best expresses theessential information jn thehighlighted sentence in

20、 thepassage Incorrect choices change the meaning inimportant waysor leave out essential information.A.We now have ample proof that ants benefit plants.B.Barbara Bentley has called for additional proof thatants benefit plants.C.In 1977 Barbara Bentley conducted research that provedthat all prior stud

21、ies were wrong.D.Proof that ants benefit plants will require many moreobservations and experiments.7.According to paragraph 4, what effect does thedestruction of the corolla have onplants.A.It leaves the seeds exposed and unprotected.B.It prevents the stigma from developing.C.It keeps pollen grains

22、from attaching properly.D.It prevents the flower from attracting pollinators.8.The word devour in the passage is closest in meaningtoA.attack.B.eat.C.damage.D.prefer.9.What role does paragraph 5 play in the passage?A.It offers various kinds of evidence for theprotectionist view.B.It presents the stu

23、dy that first proved that antsbenefit plants.C.It explains how insects find sources of nectar.D.It presents information that partly contradicts theprotectionist view.10.The word vulnerable in the passage is closest inmeaning toA.numerous.B.harmful.C.open to attack.D.difficult to locate.11.According

24、to paragraph 5, what did Bentley scomparative study show?A.Many more plants grew in places where ants werepresent than where they were absent.B.The ants preferred plants with low seed production toplants with high seed production.C.The plants occupied by ants produced many more seedsthan those that

25、were not occupiedby ants.D.The plants that grew in places without ants were muchsmaller and weaker than those thatgrew in places where antswere present.12.According to paragraph 5, ants defend morning gloryplants from seed beetles ineach of the following ways EXCEPT ：A.driving adult beetles off the

26、plants by nipping attheir feet.B.catching and eating adult beetles.C.eating beetle eggs they find on developing fruits.D.making it difficult for beetles to lay eggs ondeveloping fruits.13. Look at the four squares that indicate wherethe following sentence could beadded to the passage. Wherewould the

27、 sentence best fit? Sometimes they capturetheinsects to feed their protein-hungry larvae.Ants are portably the most frequent and certainly themost persistent defenders of plants. 【 A】 Since the highlyactive worker ants require a great deal of energy, plantsexploit thisneed by providing extrafloral n

28、ectar thatsupplies ants with abundant energy. 【 B】 Toreturn thisfavor, ants guard the nectaries, driving away or killingintruding insects that mightcompete with ants for nectar. 【C】 Many of these intruders are herbivorous and wouldeatthe leaves of the plants. 【 D】14. Directions ： An introductory sen

29、tence for a briefsummary of the passage of thepassage is provided below.Complete the summary by selecting the THREE answerchoicesthat express the most important ideas in the passage. Someanswer choicesdo not belong in the summary because theyexpress ideas that are not presented inthe passage or arem

30、inor ideas in the passage. This questions is worth 2 points.Many plants have extrafloral nectaries that producenectar even during periods inwhich the plant is not flowering.A.Evolutionary history shows that plants that produceextrafloral nectar originated in thetropics.B.Extrafloral nectar has a hig

31、her concentration of sugarthan floral nectar and is moreattractive to ants and otherinsects.C.The protectionist hypothesis is that extrafloralnextar attracts ants, and that the ants, inorder to preservethis energy-rich food source, attack insects that might harmthe plant.D.Evidence accumulated durin

32、g the twentieth centuryproved that ants provide significantbenefits for plants withextrafloral nectaries.E.Research has shown that American morning glory plantsthat are protected by ants producesignificantly more seedsthan morning glory plants that are not protected by ants.F.Ants generally ignore small insects, but they will eatthe adults of large insect species aswell as their eggs andlarvae.托福阅读答案1.B2.B3.A4.D5.A6.A7.C8.B9.B10.C11.C12.A13.C14.CDE