托福阅读试题考前辅导2017年托福阅读试题考前辅导治学有三大原则：广见闻，多阅读，勤实验。以下是小编为大家搜索整理的2017年托福阅读试题考前辅导，希望能给大家带来帮助!更多精彩内容请及时关注我们应届毕业生考试网!Moltingisoneofthemostinvolvedprocessesofabird'sannuallifecycle.Notwithstandingpreeningandconstantcare,themarvelouslyintricatestructureofabird'sfeatherinevitablywearsout.Alladultbirdsmolttheirfeathersatleastonceayear,anduponcloseobservation,onecanrecognizethefrayed,raggedappearanceoffeathersthatarenearingtheendoftheirusefullife.Twodistinctprocessesareinvolvedinmolting.Thefirststepiswhentheold,wornfeatherisdropped,orshed.Thesecondiswhenanewfeathergrowsinitsplace.Wheneachfeatherhasbeenshedandreplaced,thenthemoltcanbesaidtobecomplete.This,however,isanabstractionthatoftendoesnothappen:incomplete,overlapping,andarrestedmoltsarequitecommon.Moltrequiresthatabirdfindandprocessenoughproteintorebuildapproximatelyone-thirdofitsbodyweight.Itisnotsurprisingthatabirdinheavymoltoftenseemslistlessandunwell.Butfarfrombeingrandom,moltiscontrolledbystrongevolutionaryforcesthathaveestablishedanoptimaltimeandduration.Generally,moltoccursatthetimeofleaststressonthebird.Manysongbirds,forinstance,moltinlatesummer,whenthehardworkofbreedingisdonebuttheweatherisstillwarmandfoodstillplentiful.Thisiswhythewoodsinlatesummeroftenseemsoquiet,whencomparedwiththeexuberantchorusesofspring.Moltoftheflightfeathersisthemosthighlyorganizedpartoftheprocess.Somespecies,forexample,beginbydroppingtheoutermostprimaryfeathersoneachside(toretainbalanceintheair)andwaituntilthereplacementfeathersareaboutone-thirdgrownbeforesheddingthenextoutermost,andsoon.Othersalwaysstartwiththeinnermostprimaryfeathersandworkoutward.Yetotherspeciesbegininthemiddleandworkoutwardonbothsides.Mostducksshedtheirwingfeathersatonce,andremainflightlessfortwoorthreeweekswhilethereplacementfeathersgrow.1.Thepassagemainlydiscusseshow(A)birdsprepareforbreeding(B)birdfeathersdifferfromspecies(C)birdsshedandreplacetheirfeathers(D)birdsareaffectedbyseasonalchanges2.Theword"Notwithstanding"inline2isclosestinme