大學(xué)英語(yǔ)六級(jí)聽(tīng)力大學(xué)英語(yǔ)六級(jí)聽(tīng)力-49大學(xué)英語(yǔ)六級(jí)聽(tīng)力-49(總分：252.00，做題時(shí)間：90分鐘)一、SectionA(總題數(shù)：4，分?jǐn)?shù)：105.00)（分?jǐn)?shù)：35.00）A.B.C.D.√解析：[解析]W:Icanhardlybreathe．Wouldyoupleaseputyourcigaretteout?M:I’msorrythatI’mbotheringyou．butthisisthesmokingsection．Whydon’tyouaskthestewardesstochangeyourseat?Q:Whatdoesthemanthinkthewomanshoulddo?[解析]選D，綜合推斷題。女士要求男士把煙熄掉，男士表達(dá)了歉意，但他說(shuō)他是在吸煙區(qū)吸煙，所以他建議女士換個(gè)座位，由此可知，男士認(rèn)為女士應(yīng)該去飛機(jī)的其他地方坐，故選D。A.B.C.√D.解析：[解析]M:It’shot!Iwishitwouldrainandcooloff!W:Thisisn’tusualforNovember．Idon’trememberiteverbeingSOhotanddryinNovemberbefore．Q:WhatistheweatherusuallylikeinNovember?[解析]選C，綜合推斷題。男士說(shuō)他不記得以前的11月份有那么熱、那么干燥，由此推斷，平常的11月份天氣比目前要涼爽、濕潤(rùn)，故選c。[考點(diǎn)]·cooloff此處意為“變涼”，其他與cool相關(guān)的常見(jiàn)短語(yǔ)還有：①cool(sb./sth．)down(使某人/某物)變涼，例如：Astheweathercoolsdown．theindoorgamesheatup．隨著天氣的轉(zhuǎn)涼，室內(nèi)運(yùn)動(dòng)開(kāi)始升溫。②cool(sb.)down/off(使某人)冷靜或降低熱情，例如：Adayoncampusmaycoolthestudentsoff一天的校園生活可能使學(xué)生們冷靜下來(lái)。A.B.C.D.√解析：[解析]W:It’sgoodtoseethesunoutagaill-abigimprovementonwhatwe’vebeenhavinglately．M:Butit’ssupposedtobecloudythisevening．Q:Whatwouldtheweatherbelikethisevening7[解析]選D，信息明示題。男士說(shuō)今晚應(yīng)該是陰(cloudy)天，而選項(xiàng)D中的overcast意為“陰的，多云的”，與cloudy同義，故選D。A.B.C.√D.解析：[解析]W:I’dliketoexchangethisgreentablecloththatIboughtlastweekfortheredOne．M:Let’sseenow．Theredoneisonly$10.90．a(chǎn)ndthegreenonewas$15.Q:Howmuchmoneydoesthesalesmanowethewoman7[解析]選C，綜合推斷題。女士想把綠色的桌布換成紅色的，男士說(shuō)紅色的只要10.90美元，而綠色的則是15美元，計(jì)算可知，男士應(yīng)該找給女士4.10美元，故選C。[考點(diǎn)]·exchangeAforB意為“將A換為B”，與exchange相關(guān)的短語(yǔ)搭配還有：①exchangesth.(withsb.)(和某人)交換某事物，例如：I’dliketoexchangeseatswithyou．我想和你調(diào)換座位。②exchange(angry，etc)words爭(zhēng)論，爭(zhēng)吵，例如：Thecoupleexchangedangrywordsinfrontoftheirfriends．這對(duì)夫妻在朋友面前爭(zhēng)吵了起來(lái)。A.B.C.D.√解析：[解析]W:Hi，John，haven’tseenyouforquiteafewdays．Iheardyou’vebeensick．Howareyoufeelingnow?M:Theymustconfusemewithmybrother，Jack．Anyway，heisfeelingbetternow．Q:Whatdowelearnfromtheconversation?[解析]選D，綜合推斷題。女士說(shuō)聽(tīng)說(shuō)男士生病了，問(wèn)他現(xiàn)在怎么樣，男士說(shuō)他們一定是把他和他弟弟杰克弄混了，杰克現(xiàn)在好多了，由此推斷，生病的是男士的弟弟杰克，男士即約翰并沒(méi)有生病，故選D。（分?jǐn)?shù)：21.00）A.B.C.√D.解析：[解析]M:Iwanttofindapart-timejobduringthesummervacationandearnsomemoney．Howaboutyou?W:I’mgoingtotakeafewsummercoursessothatIcangraduateearlynextyear.Q:Whatarethespeakersmainlytalkingabout?[解析]選C，綜合推斷題。男士說(shuō)自己打算暑假做兼職賺錢，女士則打算為了明年早點(diǎn)畢業(yè)而去上暑期班，由此推斷，他們是在討論如何安排假期，故選C。A.√B.C.D.解析：[解析]W:Canweeatsomewhereelse?Veryfewsmallrestaurantslikethisservegoodfood．M:Iknow．butthereisn’tanywhereelseinthistown．Look!Thewaiteriscomingoverforourorder．Q:Whatdothespeakersthinkabouttherestaurant?[解析]選A，綜合推斷題。女士說(shuō)，像這樣的小餐館很少有能提供好的食物的，男士說(shuō)自己知道，可城里沒(méi)有別的地方可去了，由此推斷，他們覺(jué)得所在餐館的食物可能不好吃，故選A。A.B.C.D.√解析：[解析]W:ThereportsaysthatalldepartmentsaremakingaprofitexcepttheAsianDepartment．M:Well．Mr．Blackseemstobethewrongpersontoheadthatdepartment．Onemorewrongstepandhewillberemovedfromthatoffice．Q:Whatdowelearnfromtheconversation?[解析]選D，信息明示題。女士說(shuō)除了布萊克先生領(lǐng)導(dǎo)的亞洲部門，其他所有的部門都有盈利，故B、C錯(cuò)誤；男士說(shuō)如果布萊克先生再犯錯(cuò)，他的職位就會(huì)被別人接替，故選D。（分?jǐn)?shù)：21.00）A.B.C.D.√解析：[解析]9-11W:Hello．ThisisSusanRichardsfromChannel7News，andwe’redownhere，uh，attheCityMall，interviewingpeopleonhowtheycelebrateChristmas．And，uh，hi，whatisyourname?M:NickCarter．W:And，uh，Nick，uh．HowdoesyourfamilycelebrateChristmas?M:Wegosledding,andwegoovertomygrandparents’houseandhavedinnerwiththem．W:Well，thatisgreat，andletmeaskthisyoungman．Hi，whatisyourname?M:Johnny．W:AndJohnny．howoldareyou?M:Five．W:And，uh，doesyourfamilyeatanythingparticularforChristmas?M:Turkey…W:AndwhatdoesChristmasmeantoyou?M:Goingtomygrandma’sandmakingtheirbreakfast．W:Goingtograndma’sandmakingbreakfast．Andletmeaskanotheryoungman．Hi，whatisyourname?M:Steven．W:Okay，andSteven，whatdoesChristmasmeantoyou?M:Givingbynotexpectingtoget．W:Now．that’skindofhardforayoungmanlikeyourselfWhatdoesthatmean：Givingbynotexpecting．M:Well．onethingthatwedoissecretgiving．W:Secretgiving?Nowhowdoesthatworkinyourfamily?M:Wesneakuptotheporchofsomebodywewanttogiveto．weputthegiftwewanttogivetothem，ringthedoorbell，andhide．W:Ringthedoorbellandhide?Uh．soyou’renotexpectingsomething；youjustwanttobegeneroustosomeoneelse．Isthatright?M:Yeah．That’scorrect．W:Yeah．Well.that’sallherefromtheCityMall.Channel7reporting．9．Wheredoesthisnewsprogramtakeplace?[解析]選D，信息明示題。對(duì)話開(kāi)始女士就說(shuō)自己是來(lái)自第七頻道新聞報(bào)道的SusanRichards，現(xiàn)在在一個(gè)CityMall，由此可知節(jié)目現(xiàn)場(chǎng)是在一個(gè)購(gòu)物商場(chǎng)，與shoppingcenter同義，故選D。mall有“購(gòu)物商場(chǎng)”之意，而marketplace意思是“市場(chǎng)”。A.B.√C.D.解析：[解析]Howdoestheyoungman，Nick，celebratethisholidaywithhisfamily?[解析]選B，信息明示題。由男士所說(shuō)andwegoovertomygrandparentshouse…可知，他們會(huì)去祖父母家一起吃晚餐，因此B項(xiàng)(拜訪親密的親屬)正確。A.B.C.√D.解析：[解析]WhatsentencebestdescribesSteven’sfeelingsaboutChristmas?[解析]選C，信息明示題。steven說(shuō)圣誕節(jié)對(duì)于他來(lái)說(shuō)意味著Givingbynotexpectingtoget，然后又解釋說(shuō)，他們做的一件事就是悄悄地送人禮物——把禮物放在門口、按響門鈴然后藏起來(lái)，根本不期待得到什么。選項(xiàng)B說(shuō)朋友們?cè)谙碛镁劳聿蜁r(shí)贈(zèng)送禮物，選項(xiàng)D說(shuō)人們與朋友、家人和老師交換禮物，這兩項(xiàng)都不是Steven所要表達(dá)的意思。Steven也沒(méi)有談到與朋友和家人舉行聚會(huì)，所以A也不對(duì)。（分?jǐn)?shù)：28.00）A.√B.C.D.解析：[解析]12-15W:Hey．IhearyouandStephaniearereallygettingserious．M:Yeah．Ithinkshe’llbeimpressedwithmynewexerciseprogram．W:What?Whatareyoutalkingabout?Whatexerciseprogram?Whatdidyoutellher?M:Well，youknow，Ienjoystayinginshape．First，Igenerallygetupeverymorningat5:30a.m．W:Oh，yeah．Sincewhen?Youdon’trolloutofbeduntilatleast7:30p.m．M:No，no，andonMondaysandWednesdays…W:Ah，notanothertalltale…M：Ialmostalwaysgoioggingforaboutahalfhour，youknow，toimprovemyendurance．W:Hey．joggingtotherefrigeratorforaglassofmilkdoesn’tcount．M:Ofcourse，beforeIleave,IusuallymakesureIdosomestretchessoIdon’tpullamuscleonmyrun.W:Right．Onejumpingjack．M:Then．ItoldherthatIusuallyliftweightsTuesdaysandThursdaysforaboutanhourafterwork．W:Humph．M:Thisreallyhelpsmebuildmusclestrength．W:Aone-poundbarbell．M:Finally，IoftengohikingonSaturdayswithmydog，well，andIlikehikingbecauseithelpsmeburnoffstressandreduceanxietythatbuildsupduringtheweek．W:Ohyeah．thoselies．M:Well，uh，asforFridays，Isometimesjustrelaxathomebywatchingamovieorinvitingyouovertovisit．W:IfIbuythepizza．M:But…but…AndonSundays，Itakethedayofffromexercising，butIusuallytakemydogforawalk．W:Forgetit．She’llneverbuythisstory．12．WhatdoesthemanusuallydoonMondaysandWednesdays?[解析]選A，信息明示題。男士所說(shuō)Ialmostalwaysgojoggingfor…就是指在周一和周三經(jīng)常慢跑。解答此題的關(guān)鍵在于了解gojogging就是“慢跑”的意思，如果不明白gojogging是什么意思，可以根據(jù)后面提到的toimprovemyendurance(增強(qiáng)耐力)及…soIdon’tpullamuscleonmyrun(跑的時(shí)候不會(huì)肌肉拉傷)確定答案為A。A.B.C.√D.解析：[解析]WhatdoesthemandobeforetheactivityinQuestion1?[解析]選C，信息明示題。男士提到beforeIleave，IusuallymakesureIdosomestretches…，在離開(kāi)家出門(慢跑)之前，先做一些伸展運(yùn)動(dòng)，防止跑的過(guò)程中肌肉拉傷。選項(xiàng)D中push-up是“俯臥撐”的意思。A.√B.C.D.解析：[解析]WhydoesthemangohikingonSaturdays?[解析]選A，信息明示題。由男士所說(shuō)Ilikehikingbecauseithelpsmeburnoffstressandreduceanxiety…可知，周六去徒步旅行是因?yàn)榭梢詭椭麥p少一周產(chǎn)生的壓力和焦慮，選項(xiàng)A中的getridof就相當(dāng)于原文中bumoff。A.B.√C.D.解析：[解析]Whatcanwelearnaboutthewomanfromtheconversation?[解析]選B，綜合推斷題。男士說(shuō)早上5點(diǎn)半起床，女士則說(shuō)他至少下午7點(diǎn)半才起床；男士說(shuō)早上慢跑半個(gè)小時(shí)，女士反語(yǔ)說(shuō)不包括慢跑到冰箱取牛奶；男士說(shuō)做舉重鍛煉，女士說(shuō)舉1磅重的杠鈴；還有女士所說(shuō)的anothertalltale，thoselies，neverbuythisstory足以說(shuō)明女士認(rèn)為男士在說(shuō)謊。二、SectionB(總題數(shù)：3，分?jǐn)?shù)：70.00)（分?jǐn)?shù)：21.00）A.B.C.D.√解析：[解析]16-18Lotsofpeoplegetangryintraffic．Butsomepeoplegetreallyangry．Thishostilitycanleadtoaggressiveactionsor，insomecases，violence．Angrydrivershavebeenknowntopulloutagunorcauseacrash．Foryearspeoplehavecalleditroadrage．Nowwearehearingamedicalname．Expelssaythatinsomecases，theseactionsarelinkedtoadeeperproblem：intermittentexplosivedisorder，orI.E.D．Itmeansthatfromtimetotimepeopleexplodeinanger．Theymayattackothersordamageproperty．Medicalexpertssaythisdisorderiscausedbvanimbalanceinbrainchemicals．TheNationalInstituteofMentalHealthrecentlypaidforastudyofintermittentexplosivedisorder．ResearchersatHarvardMedicalSchoolandMassachusettsGeneralHospitalinBostonandattheUniversityofChicagodidthework．Theresearchersusedinformationfromastudyofmorethan9,000adultsintheUnitedStates．Theyfoundthatintermittentexplosivedisorderis“muchmorecommon”thanhasbeenrecognized．Theysayitaffectsasmanyas7percentofadultsatsomepointintheirlifetimes，dependingonhowwidelyitisdefined．Thestudysuggeststhattheconditionaffectsupto16millionAmericans．Itgenerallyappearsaroundtheageof14,andismorecommoninmenthaninwomen．Doctorssayitusuallybeginswithincidentsofextremeangerdirectedatfamilymembers．Theysaytheproblemismadeworseforsomebystressfrombaddrivers，longtraveltimes，crowdedroadsandbusylives．Theysayasmalltrafficproblemcancausethepersontobecomeuncontrollablyangry．16．Whatdoesthepassagemainlytalkabout7[解析]選D，主旨題。文章開(kāi)始提到，開(kāi)車時(shí)的攻擊行為或暴力行為被稱為roadrage，其醫(yī)學(xué)術(shù)語(yǔ)為intemmentexplosivedisorder(間歇性狂暴癥)，文章接下來(lái)的內(nèi)容都是圍繞I.E.D.展開(kāi)的，故選D。A.B.C.D.√解析：[解析]What’sthecauseofroadrageaccordingtothemedicalexperts?[解析]選D，綜合推斷題。文章提到，醫(yī)學(xué)專家認(rèn)為這種紊亂是由大腦中化學(xué)物質(zhì)的不均衡造成的，結(jié)合上文可知，此處的“這種紊亂”(thisdisorder)是指間歇性狂暴癥(intennittentexplosivedisorder)，~proadrage，故選D。A.√B.C.D.解析：[解析]Whichofthefollowingismorecommoninmenthaninwomenaccordingtothepassage?[解析]選A，綜合推斷題。文章提到，研究表明這種情況影響到多達(dá)1600萬(wàn)美國(guó)人，該情況通常出現(xiàn)在14歲左右，而且男性比女性更普遍，其中“這種情況”(thecondition)就是全文討論的中心內(nèi)容，間歇性狂暴癥(I.E.D.)，故選A。（分?jǐn)?shù)：21.00）A.B.√C.D.解析：[解析]19-21Identitythefthasbeenasubjectinthenewsrecently．ItisconsideredoneofthetopcrimesintheUnitedStates．TheFederalTradeCommissionestimatesthat10millionAmericansbecomevictimsofidentitythefteachyear．Identitythievesstealpersonalinformation．TheycollectSocialSecuritynumbers，bankingrecordsandtelephonenumbers．Theyusethisinformationtorequestloansorgetcreditcardsinthenameofthevictim．Identitythievesspendalotongoodsorserviceswithoutpayingforthem．F.T.C.officialsestimatemorethan52thousandmilliondollarsingoodsandserviceswerepurchasedlastyearthroughidentitytheft．Victimsofidentitytheftcanspendyearsattemptingtore-establishtheirfinancialhistoryandgoodname．Somehavebeendeniedjobsorarrestedforcrimesinwhichtheywerenotinvolved．Identitythievesuseseveralmethodstogetwhattheyneed．Theymaytrickpeopleintogivingpersonalinformationoverthetelephone．Theyalsomaystealdocumentscontainingsuchinformation．Activistgroupshavecalledfornewlawstoprotectthepublicfromidentitytheft．Recently，acommitteeoftheUnitedStatesSenatesaiditwouldholdhearingsontheissue．Twocasesofidentitythefthelpedthecommitteetocallthehearings．19．Whydoidentitythievesstealpersonalinformation?[解析]選B，綜合推斷題。文章指出，竊取個(gè)人信息的人利用偷來(lái)的身份信息以受害者的名義申請(qǐng)貸款和信用卡，他們花大量的錢購(gòu)買商品或服務(wù)，自己卻不付錢，由此可知，他們竊取個(gè)人信息是為了免費(fèi)消費(fèi)，從中漁利，故選B。A.B.C.√D.解析：[解析]Whatmayhappentothevictimsofidentitytheftaccordingtothepassage?[解析]選C，信息明示題。文章提到身份竊取的受害者要花多年時(shí)間來(lái)重建自己的財(cái)政記錄和信譽(yù)，有些人被解雇了，或因他們并沒(méi)有參與的犯罪而被捕．而被捕并不等于被關(guān)進(jìn)監(jiān)獄，故排除B，選C。A.B.C.D.√解析：[解析]Howdoidentitythievesgetpersonalinformation?[解析]選D，信息明示題。文章指出，身份竊賊可能通過(guò)打電話騙取當(dāng)事人的身份信息，或者盜竊包含此類信息的文件，故選D。社會(huì)安全號(hào)碼(SocialSecuritynumbers)．是罪犯所需信息的一部分，并非得到信息的手段，故排除A。（分?jǐn)?shù)：28.00）A.√B.C.D.解析：[解析]22-25PassageThreeMorethan1millioncollegestudentsaregraduatingthisyearintheUnitedStates．TheNationalAssociationofCollegesandEmployersresearchesthejobmarketfornewcollegegraduates．ThereportfortheClassof2023offersthebestnewsin4years．Comparedtolastyear,employersexpecttohire13percentmorenewgraduates．61percentoftheemployersinthereportsaidtheyexpecttohiremorenewgraduatesthantheyhiredlastyear．Lastyearthatnumberwasjustover50percent．Thebestchancesforjobsmaybeatmanufacturingcompanies．Thereportsaysmanufacturersexpecttoincreasetheirjobsforyoungpeoplefleshoutofcollegeby13percent．Serviceprovidersexpecta12percentincrease．Themiddleofthecountryappearstobetheareawiththemostdemand．CompaniesintheMidwestsaytheyexpecttoincreasetheirnumberofnewcollegegraduatesthisyearby26percent．Thereportsaysincreasesof15percentareexpectedinboththeWestandtheNortheast，and6percentintheSouth．TheNationalAssociationofCollegesandEmployerssayspayoffersareupthisyearinanumberofjobs．Thehighestpavingjobsareincomputersoftwaredesignanddevelopment．Theaverageofferofstartingpayisalmost54thousanddollars．Thelowestpayisforteachers,atiustunder30thousanddollars．Othertopjobsforgraduatesthisyearincludeaccountant，managementtrainee，sales，financialanalyst，constructionengineerandregisterednurse．22．Howmanynewgraduatesdotheemployerswanttohireaccordingtothepassage?[解析]選A，信息明示題。文章提到，與上一年相比，雇主期望雇用的應(yīng)屆畢業(yè)生人數(shù)多出13%，故選A。A.B.C.D.√解析：[解析]WhichpartoftheU.S.appearstoneedmostnewgraduates?[解析]選D，綜合推斷題。文章提到，中部地區(qū)是需要人數(shù)最多的地方，結(jié)合上文可知，此處需要的是應(yīng)屆畢業(yè)生，故選D。文章接著提到，中西部地區(qū)的公司對(duì)應(yīng)屆畢業(yè)生的需求將增長(zhǎng)26%，西部和東北部將增長(zhǎng)15%，南部增長(zhǎng)6%，可見(jiàn)增長(zhǎng)最多的就是中西部地區(qū)，由此也可確定答案為D。A.B.C.√D.解析：[解析]Whichofthefollowingisthehighestpayingjob?[解析]選C，信息明示題。文章指出，收入最高的是電腦軟件設(shè)計(jì)和開(kāi)發(fā)方面的工作。由此可知，電腦軟件設(shè)計(jì)師或開(kāi)發(fā)者收入最高，故選C。A.B.C.D.√解析：[解析]Whichpositionwouldthegraduatesnotliketotakeinviewofthepay?[解析]選D，綜合推斷題。文章指出，收入最低的是教師，由此可知，如果考慮到工資因素，應(yīng)屆畢業(yè)生可能不想去作教師，故選D。三、SectionC(總題數(shù)：1，分?jǐn)?shù)：77.00)Fiveoutoftenoftheworld’slargestfoodcompaniesareaggressivelyexploringthepotentialofnanotechnologyforbetterpackaging,improvedfoodsafetyandbetternutritionalcontent.Thefoodindustryismovingfasterthananyothersectorto(26)nanotechnology--themanufactureofobjectssosmallthattheycannotbeseenevenwitha(27)microscope--anditisestimatedthatitwillbe(28)into＄20billion(￡11billion)worthoffoodproductsby2023.Butdothepublicwanttheirfoodengineered?Theexperiencewithgenetically(29)(GM)foodwouldsuggestnot.Althoughnonanotechfoodproductsare(30)inBritain,ahandfulareintheUSwheretherearealreadydemandsfromlobbygroupsfor”nanohazard”labeling.Thereislittlecontroversyovernewtechniquesof(31)nanoscale-sensingdevicestofoodproductsandpackaging,sothatthesourcesoffood(32)canbetracedbacktoorigin;somethingthatfood(33)havelongbeendemanding.Couldnanomaterialsmigratefrompackagingintofood?Ifso,whatmighttheirimpactbe?(34)(FSA).Sothatisoneareawherefuturecontroversymaylie.(35).ButwhiletheGovernmentclaimsthatitisproceedingwithnanotechnologyusinganevidence-basedapproach,(36)TheGovernmentneedsamoreactiveapproach,pushingstudiesahead.Fiveoutoftenoftheworld’slargestfoodcompaniesareaggressivelyexploringthepotentialofnanotechnologyforbetterpackaging,improvedfoodsafetyandbetternutritionalcontent.Thefoodindustryismovingfasterthananyothersectorto(26)nanotechnology--themanufactureofobjectssosmallthattheycannotbeseenevenwitha(27)microscope--anditisestimatedthatitwillbe(28)into＄20billion(￡11billion)worthoffoodproductsby2023.Butdothepublicwanttheirfoodengineered?Theexperiencewithgenetically(29)(GM)foodwouldsuggestnot.Althoughnonanotechfoodproductsare(30)inBritain,ahandfulareintheUSwheretherearealreadydemandsfromlobbygroupsfor”nanohazard”labeling.Thereislittlecontroversyovernewtechniquesof(31)nanoscale-sensingdevicestofoodproductsandpackaging,sothatthesourcesoffood(32)canbetracedbacktoorigin;somethingthatfood(33)havelongbeendemanding.Couldnanomaterialsmigratefrompackagingintofood?Ifso,whatmighttheirimpactbe?(34)(FSA).Sothatisoneareawherefuturecontroversymaylie.(35).ButwhiletheGovernmentclaimsthatitisproceedingwithnanotechnologyusinganevidence-basedapproach,(36)TheGovernmentneedsamoreactiveapproach,pushingstudiesahead.（分?jǐn)?shù)：77.00）填空項(xiàng)1:__________________（正確答案：embrace）解析：[解析]26-36Fiveoutoftenoftheworld’slargestfoodcompaniesareaggressivelyexploringthepotentialofnanotechnologyforbetterpackaging，improvedfoodsafetyandbetteinutritionalcontent．Thefoodindustryismovingfasterthananyothersectorto(26)embracenanotechnology--themanufactureofobjectssosmallthattheycannotbeseeneverwitha(27)conventionalmicroscope--anditisestimatedthatitwillbe(28)incorporatedinto$20billion(￡1lbillion)worthoffoodproductsby2023．B