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villeflyingfirst,thebrotherstookturnsaspilot,andtheyflewthreemoretimesthatday.Ontheirfourthtry,theymanagedtogo852feetin59seconds枣anamazingfeatatthetime.Thetwobrothershadinventedpoweredflight.
OrvilleandWilburWrightownedabicycleshopinDayton,Ohio.Althoughtheyhadnotgonetoschooltolearnaboutairplanesorengineering,theyweregoodmechanics.Byrepairingbicycles,theyhadlearnedhowgearsandpulleysworked.Theyalsolearnedtotakecarefulnotesaboutwhattheysaw.Eachtimetheymadeanewdesignandtestedamachine,theytooknotesandmadedrawings.Theywouldstudythesetofigureoutwhattheycoulddobetterthenexttime.
BeforetheWrightbrothersflew,theydidmanythingstoprepareforthisextraordinaryachievement.Theyreadeverythingtheycouldfindaboutair,balloons,andkites.Thentheymadecarefulsketchesofwhattheywantedtobuild.Theybeganbymakingmodelkitestolearnhowairflowedoverwings.Theymadethembiggerandbiggeruntiltheyhadagliderakitethatisbigenoughtoholdaperson,butwithnoengine.TheWrightbrothersmadethreeglidersbeforebuildingtheirfirstairplane.Eachtimetheymadeaglider,theywouldtestit,makecarefulobservations,andthenimprovetheirdesign.
Whentheymadeagliderthatflewwell,theyaddedanengine.Thisstepwasharderthanitsounds,becausetheyhadtofindanenginethatwasbothlight-weightandpowerful.Theenginesthattheycouldbuywereeithertooheavyortooweak,sotheyaskedtheirfriendCharlieTaylortohelpthembuildone.ThefirstenginethatCharliebuiltbrokealmostimmediately,butthesecondoneworkedwell.
AfterOrvilleandWilburinstalledtheengineintheirplane,theywerealmostready.Theysimplyhadtowaitfortheperfectdaywithjustthefightamountofwind.OnthemorningofDecember17,1903,theyhadtheirchance.Andtheairplaneflewintohistory.
36.Whatwasthespeedofthefirstflight
A.10feetpersecond.B.120feetperminute.
C.12feetpersecond.D.1200feetperhour.
37.WhatcanwelearnabouttheWrightbrothersfromParagraph2
A.Theyhadlittleformaleducation.
B.Theyownedasuccessfulbusiness.
C.Theywereverythoroughintheirwork.
D.Theyhadexperiencedmanyfailures.
38.Thebrothersconstructedanumberofkitesinorderto_________.
A.testthematerialstheywouldusefortheirplane
B.provethatbuildingaflyingmachinewaspossible
C.seewhichshapecouldsupportthemostweight
D.improvethedesignoftheirplane'swings
39.Whichofthefollowingistrueaccordingtothepassage
A.TheWrightbrothersbuiltallthepartsoftheirfirstplane.
B.WilburWrightflew852feetonDecember17,1903.
C.TherewasnowindonthedaytheWrightbrothersflew.
D.OrvilleWrightwentontobeeaprofessionalpilot.
40.Inwhatorderdidthefollowingeventsoccur
a.TheWrightbrothersstartedreadingaboutballoons.
b.TheWrightbrothersranabicyclerepairshop.
c.Asuitableenginewasbuilt.
d.Orvillesuccessfullyflewforthefirsttime.
e.CharlieTaylorwasaskedtohelp.
f.Threegliderswerebuilt.
A.c,f,e,b,a,dB.b,c,a,f,d,e
C.b,a,f,e,c,dD.d,e,a,f,c,b
D
Expensiveperfumes(香水)eintinybottles,butmanyhideawhale-sizedsecret.
Toperfectaparticularsmell,perfume-makersoftenuseaningredientthatesfromspermwhales,calledambergris.Butusingambergris,whichhelpsaperfumelastlonger,isstronglyopposedbymanypeoplewhothinkitiswrongtokillwhalesjustsowecansmellsweet.JoergBohlmannisneitheraperfumernorawhaleexpert.He'saplantbiologistattheUniversityofBritishColumbiainCanada.Buthisdiscoveryofanewplantgene(基因)mightpushwhalesoutoftheperfumebusiness.
Thegeneesfromfirtrees,foundthroughoutNorthAmericaandmonlyusedasChristmastrees.Thetreesproduceachemicalthatcanbeusedinperfumeinplaceofambergris枣butwithacatch.
"There'saproblemthatmanypeoplewouldn'tconsider.Inthetree,thechemicalismixedwithmanyothers.Thatmakesseparationachallenge,"Bohlmannsays."It'sliketryingtoisolatesugarfromabiscuit."
Thisiswheresciencebeesuseful.WhenBohlmannlearnedthatfirtreesproducetheambergris-likechemical,hedecidedtousehisgeneknow-howtofindtheinstructionsforhowtomaketheambergris-substitute.www.xkb1.
Bohlmannfoundthatgeneandtookitoutofthetreecells.Thenhedidsomethingthatmightsoundstrangetosomeonewhodoesn'tworkingeics:Bohlmannputthegenefromthetreeintoyeast(酵母)cells.
Yeastmaysoundfamiliarbecauseit'susedtomakethingslikebread,wineandbeer.Biologistsliketoworkwithyeastbecauseiteasilyadoptsnewgenesandchangesitsfeaturesandbehaviour.WhenBohlmannputthefirtreegeneintotheyeast,theyeaststartedmakingthesamechemicalthathadbeenproducedbythetree.
Perfumerspaybigmoneyforambergrisbecauseitisafixative,whichmeansitholdsasmellinplaceonaperson'sbody.
"Cheapperfumessmellgoodinthefirsthourorsoandtheneverythingisgone,"explainsBohlmann."Butexpensiveperfumesaremuchmorestable.Theirsmelllastsmuchlonger,forhoursorevenadayafteryouapplythem."
Thenewchemical,madefromthetreegenes,canbeusedasafixative,too.Andusingyeasttomakeitisfarcheaperthanacquiringambergris.
Bohlmannadmitsheneverthoughthe'dgetintotheperfumebusiness.Butnow,hesays,producershavebeencallingtofindouthowtousehistechnologyinnewperfumes.
41.Itcanbeinferredfromthepassa
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