历年托福考试阅读高频真题汇总【含答案】

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1、智课网TOEFL备考资料历年托福考试阅读高频真题汇总【含答案】摘要：之前我们已经上传了历年来托福阅读考试的真题题目，今天小编接着为大家介绍一些托福阅读考试过程中经常遇到的一些真题类型，这些题目全部是精华内容，非常值得大家拥有。历年托福考试阅读高频真题依次从上到下，出题频率由高到低，下面我们现将其中的一篇出题率极高的文章内容分享给你。Iffoodisallowedtostandforsometime,itputrefies.Whentheputrefiedmaterialisexaminedmicroscopically,itisfoundt

2、obeteemingwithbacteria.Wheredothesebacteriacomefrom,sincetheyarenotseeninfreshfood?Evenuntilthemid-nineteenthcentury,manypeoplebelievedthatsuchmicroorganismsoriginatedbyspontaneousgeneration,ahypotheticalprocessbywhichlivingorganismsdevelopfromnonlivingmatter.Themostpowerf

3、ulopponentofthetheoryofspontaneousgenerationwastheFrenchchemistandmicrobiologistLouisPasteur(1822-1895).Pasteurshowedthatstructurespresentinaircloselyresemblethe.microorganismsseeninputrefyingmaterials.Hedidthisbypassingairthroughguncottonfilters,thefibersofwhichstopsolidp

4、articles.Aftertheguncottonwasdissolvedinamixtureofalcoholandether,theparticlesthatithadtrappedfelltothebottomoftheliquidandwereexaminedonamicroscopeslide.Pasteurfoundthatinordinaryairtheseexistsavarietyofsolidstructuresranginginsizefrom0.01mmtomorethan1.0mm.Manyofthesebodi

5、esresembledthereproductivestructuresofcommonmolds,single-celledanimals,andvariousothermicrobialcells.Asmanyas20to30ofthemwerefoundinfifteenlitersofordinaryair,andtheycouldnotbedistinguishedfromtheorganismsfoundinmuchlargernumbersinputrefyingmaterials.Pasteurconcludedthatth

6、eorganismsfoundinputrefyingmaterialsoriginatedfromtheorganizedbodiespresentintheair.Hepostulatedthatthesebodiesareconstantlybeingdepositedonallobjects.Pasteurshowedthatifanutrientsolutionwassealedinaglassflaskandheatedtoboilingtodestroyallthelivingorganismscontaminatingit,

7、itneverputrefied.Theproponentsofspontaneousgenerationdeclaredthatfreshairwasnecessaryforspontaneousgenerationandthattheairinsidethesealedflaskwasaffectedinsomewaybyheatingsothatitwouldnolongersupportspontaneousgeneration.Pasteurconstructedaswan-neckedflaskinwhichputrefying

8、materialscouldheheatedtoboiling,butaircouldreenter.Thebendsintheneckpreventedmicroorganis