标准的 PCR过程一般分为变性、复性、延伸三大步,这三大步需要的温度依次是 ()
A
暂无解析
Our()sensitivitydecreaseswithage.Byage60,mostpeoplehavelost40percentoftheirabilitytosmelland50percentoftheirtastebuds.
Passage3
Questions11to15arebasedonthefollowingpassage:
TheideaofaspecialdaytohonormotherswasfirstputforwardinAmericain1907.twoyearslaterawoman,Mrs.JohnBruceDodd,inthestateofWashingtonproposedasimilardaytohonortheheadofthefamily—thefather.Hermotherdiedwhenshewasveryyoung,andherfatherbroughtherup.Shelovedherfatherverymuch.
InresponsetoMrs.Dodd’sideathatsameyear—1909,thestategovernorofWashingtonproclaimed(宣布)thethirdSundayinJuneFather’sDay.TheideawasofficiallyapprovedbyPresidentWoodrowWilsonin1916.in1924,PresidentCalvinCoolidgerecommendednationalobservanceoftheoccasion“toestablishmoreintimate(亲密)relationsbetweenfathersandtheirchildren,andtoimpressuponfathersthefullmeasureoftheirobligations.”TheredorwhiteroseisrecognizedastheofficialFather’sDayflower.
Father’sDaytooklongertoestablishonanationalscalethanMother’sDay,butastheideagrainedpopularity,tradesmenandmanufacturersbegantoseethecommercialpossibilities.Theyencouragedsonsanddaughterstohonortheirfatherswithsmallthank-youpresents,suchasatieorpairofsocks,aswellasbysendinggreetingcards.
DuringtheSecondWorldWar,AmericanservicemenstationedinBritainbegantorequestFather’sDaygreetingcardstosendhome.ThisgeneratedaresponsewithBritishcardpublishers.ThoughatfirsttheBritishpublicwasslowtoacceptthisratherartificialday,it’snowwellcelebratedinBritainonthethirdSundayinJuneinmuchthesamewayasinAmerica.
Father’sDayseemstobemuchlessimportantasoccasionthantheMother’sDay.Notmanyofthechildrenoffertheirfatherssomepresents.ButtheAmericanfathersstillthinktheyaremuchbetterfatedthanthefathersofmanyothercountries,whohavenotevenadayfortheirsakeinnameonly.
11.WhendidFather’sDayofficiallybegintohavenationalpopularity?
A.1907B.1909C.1916D.1924
12.WhofirststartedtheideaofholdingtheFather’sDay?
A.Mrs.JohnBruceDoddB.Mrs.JohnBruce’sMother
C.ThegovernmentofWashington.D.Somebusinessmen.
13.WhatflowerwillbepopularonFather’sDay?
A.LilyB.WaterLilyC.RedroseorwhiteroseD.Sunflower.
14.Whichstatementistrue,aaccordingtothispassage?
A.IttookevenlongerforMother’sDaytogainnationalpopularity.
B.ThebusinessmenhelpedtomakeFather’sDaypopular.
C.Father’sDayisonlycelebratedinAmerica.
D.Father’sDayisonlyatrickofthebusinessmentomakemoney.
15.WhatwasthefirstreactionoftheBritishpublishingtowardsFather’sDay?
A.Theythoughthighlyofitandaccepteditatonce.
B.Theyjustaccepteditatoncewithoutanyhesitation.
C.Theyjustthoughtitajoke.
D.Theythoughtitwastooartificialandtookalongtimetoaccept.
You____thatlettertoJames.However,youdidn't.
Urbancongestionwouldgreatlyberelievedifthe____chargedonpublictransportweremorereasonable.