正确360问答答案：C

Thisroomi厂积sdevotedtoelectricfish.[29]T容治底乙空总王领助怎留hefishinthetankbehindmeca帝升统啊代nproduceastrongjoltofelectricityt华乱末食激农倍助oshockitsprey,butmostofthefishinhereproduceonlyweakelectricalimpulsesthatareusefulfornavigating,locatingfood,andevenforcommunicating.械关入歌社煤酒也Theknifefishisagoodexample.Thisfishnavigatesusingtinyreceptorsinth制凯久技区印措块约武eskinthata去尽带白济艺风胡李resensitivetoelectricalimpulses.[30]Thekn罪答照色ifefishproducesanelectricalsignal,andthereceptorsinitsskinletitknowwhenthesig促差黑父切nalisdistortedbyatreeroot,orsomeotherobstac群le,soitcangoaroundit.Fishalsousetheabilitytop东七钱位营连贵roduceanddetectelectricalimpul完事巴德衣第弦蒸写sestocommunicate.Theycantelleachotherwhatspeciestheybelongto,howbigtheyare,andwhethertheyremaleorfemale.[3器钱密二始给侵检济规1]Wehaveatankherethatsspeciallyequippedtoconverttheinaudiblesignalsthefishproducei见简陈背结重袁察适ntosoundsyoucanhearwhenyouputontheseheadphones.Iurgeyoualltolisteninwhen指李景仍志练销同节工Imdonespeaking.Nowhav力仍端套缺助或川或整ealookatthee在少至侵席来lectricrays.Raysareespeciallyinterestingtomed年威德保晚格列通另icalresearchersbecauseoftheorganstheyusetoproduceelectricity.Theseorganscontainachemicalthatcarriessignalsfromonenerveendingtothenext,notonlyinrays,butalsoinpeople.Bystudyingtheseorgans,scientistshopetolearnmoreaboutdiseasesthatinterruptthetransmissionofimpulsesfromonenervetoanother.29.Whatisthetalkmainlyabout?30.Whatdoestheknifefishuseelectricityfor?31.Whydoesthespeakersuggestputtingonheadphones?【解题思路】四项均提到了鱼，而且很可能与发电鱼有关。【解析】短文开头说这是个用于研究发电鱼的房间，然后介绍说后面鱼缸里的鱼可以产生强电流使猎物休克，但大多数的鱼只能发出对导航、确定食物甚至交流有用的弱电流。短文后面分别介绍了这几种应用，因此本篇短文主要谈的是一些鱼怎样运用电流，故选C。

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