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时间:2019-02-26
《历年托福考试阅读高频真题汇总【含答案】》由会员上传分享,免费在线阅读,更多相关内容在应用文档-天天文库。
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
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