【TheCabbageWhitebutterfly（菜粉蝶）hasanaturalrangeacrossEurope，Asia，andNorthAfrica．Tomanyfarmers，thebutterfliesareregardedasapest（害虫）；toothers，theyareprettytolookat．Researchersarelookinginton】
TheCabbageWhitebutterfly（菜粉蝶）hasanaturalrangeacrossEurope，Asia，andNorthAfrica．Tomanyfarmers，thebutterfliesareregardedasapest（害虫）；toothers，theyareprettytolookat．Researchersarelookingintonewwaystomakeefficientphotovoltaic（光电的）energyandforthistheyhavebeeninspiredbythev-shapepostureoftheCabbageWhitebutterfly．Photovoltaicenergyisthesciencebehindsolarpower，wherelightisturnedintoelectricity．
Toimprovethecollectionofsunlight，aresearchgrouphavebeeninspiredbytherestingpostureoftheCabbageWhitebutterfly．Thebutterflykeepsa"v"shapeinordertoheatupitsflightmusclesbeforetakingoff．Bycreatingsolarpanels（板）inthisshape，scientiststhinkthatthequantityofpowerthatasolarpanelcanusecanbeincreasedbyaround50percent．
Thecrucialpartistheweightofsolarpanels．Forthistheresearchersdevelopedakindofmaterialthatislightweight．TheCabbageWhitebutterflyisdifferenttomanyotherbutterfliesbecauseitisusingthev-formation．Oncloudydayscommonbutterfliesneedtowaittoreceiveenoughsunlightinordertofly．However，byowningthev-shapeposturetheCabbageWhitebutterflyisabletoreceivemoreenergymorequicklythanotherbutterflies．Inaddition，thebutterflycanflashbacksunlightfromitswings，whichallowsitsflightmusclestobewarmeduptothebesttemperature．
ThenewresearchwasdoneattheUniversityofExeter'sEnvironmentandSustainabilityInstitute（ESI）．Discussingthefindings，leadresearcherProfessorTapasMallickstated："Thisengineeringisnotnew．However，thisresearch，whichshowswaystodeveloplow-costsolarpower，hasnotbeendonebefore．"
19．Whatdoestheunderlinedword"crucial"inParagraph3mean？___
A．Important．B．Easy．C．Useful．D．New．
20．Whichisthemainbenefitofthebutterfly'sv-shapewings？___
A．Theyalwayskeepthebutterflywarm．
B．Theycanhelpthebutterflyflymuchhigher．
C．Theycanhelpthebutterflyavoiddanger．
D．Theycanhelpthebutterflygetmoresunlight．
21．Commonbutterfliesneedtowaitoncloudydaysbecause___．
A．theywaittogetenoughwind
B．theyl