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1、Unit15Learning单元检测B——阅读理解提速练Ⅰ.阅读理解A(2018·湖北省鄂西北联考)Ithappenstomostfirsttimefishkeepers.Theyruntoafishstore,pickoutthebestlookingfish,andgetallthethingstheyneedfortheirtanks.Thentheyfilluptheirtanksandputtheirfishinthewater.Overthecourseofthenextweek,theirfishar
2、en'tlookingsogood.Thenallofasudden,alloftheirfishstarttodieoff.Luckily,thereisanexplanation.Ammonia(氨)andnitrite(亚硝酸盐)aretoxictofish.Yousee,keepingfishinatankproducesammonia.Ifafishisplacedinanewtank,thetankwon'tbeequippedwiththeabilitytochangethatammoniaintoa
3、lessharmfulchemical.Andthat'swhytheydie.Toavoidthewholefailure,youhavetounderstandalittlesomethingcalledtheNitrogenCycle(氮循环).Afterammoniaisproducedinatank,akindofbacteriumthatisnaturallyfoundinwater(abacteriumthatconsumesammoniaandproducesnitrite)reproducesit
4、selftoformalargeenoughareatochangeallammoniaintonitrite.Astheconcentration(浓度)ofnitriteincreases,thesamethinghappenstonitrite,whichhappenedtoammonia.Agroupofbacteriathatchangenitriteintonitrate(硝酸盐)forminlargenumbers.Thecycletakesaboutoneweektoseveralmonths,de
5、pendingonyourtechnique.Whenatankreachesapointwhereitcanchangeallammoniaandnitritebeingproducedinatanktonitratebeforetheyreachharmfulconcentrations,ithasfinishedtheNitrogenCycle—itissafeforfish.Sobeforeyoueverplaceafishintoatankfromnowon,usesomeskillstomakeitdo
6、thatfirst.Todoso,slightlyincreaseammoniaconcentrationofyourtank.Ifafter24hours,yourtankhasnomarkofammoniaornitrite,youcanensurethatit'scycled.Youjustneedtoperformapartialwaterchangeandyourtankisreadyforfish.语篇解读：本文是说明文。新手养鱼经常遇到这样的问题：他们刚养不久的鱼相继死去。这是因为新鱼缸没有经过氮循环
7、，从而导致鱼中毒死亡。1．WhatcanwelearnfromPara.1?A．It'sreallyhardforpeopletokeepfishwell.B．Theauthorfeelsverysorryforthosedeadfish.C．Newfishkeepersbegintoraisefishinahurry.D．Peoplehavenoideahowtousetheirtankswell.解析：选C 推理判断题。第一段描述了养鱼新手经常会遇到的问题：他们刚养的鱼很快就死了；由第二段的最后两句可知这是因为
8、新买的鱼缸没有经过氮循环，从而导致鱼中毒而死；由此可推知，作者在第一段中想说明新手养鱼太仓促了。2．Whichofthefollowingcanreplacetheunderlinedword“toxic”inPara.2?A．Open. B．Harmful.C．Familiar.D．Beneficial.解析：选B 词义猜测题。由第二段的“th
