题目内容：
回答题：TheWorld'sBest-SellingMedidne Sinceancienttimes,peopleallovertheworldhaveusedwillowtostoppain．Thewillowtreecontainssalicylicacid(水杨酸)．Thisstopspain,butthereisoneproblem．Salicylicacidalsohurtsthestomach．In1853,aFrenchscientistmadeamixturefromwillowthatdidnothurtthestomach．However,hismixturewasdifficulttomake,andhedidnottrytoproduceorsellit.
In1897,inGermany,FelixHoffmannalsomadeamixturewithsalicylicacid．Hetriedithimselffirstandthengaveittohisfatherbecausehisfatherwasoldandinalotofpain.Hisfather'spainwentaway,andthemixturedidnothurthisstomach.
HoffmannworkedforBayer,aGermancompany．Heshowedhisnewdrugtohis manager,whotestedthedrugandfoundthatitworkedwell.Bayerdecidedtomakethedrug.TheycalleditaspirinandputtheBayernameoneverypill.
Aspirinwasanimmediatesuccess．Almosteveryonehaspainofsomekind,soaspirinansweredatrueneed．Aspirinwascheap,easytotake,andeffective．Italsoloweredfevers.Aspirinwasawonderdrug.
Atfirst,Bayersoldthedrugthroughdoctors,whothesoldittotheirpatients．In1915,thecompanystartedtosellaspirinindrugstores:IntheUnitedStates,Bayerhadapatent(专利)onthedrug．Othercompaniescouldmakesimilarproductsandselltheminothercountries,butonlyBayercouldmakeandsellaspirinintheUnitedStates．Intime,BayercouldnolongerownthenameaspirinintheUnitedStates．Othercompaniescouldmakeitthere,too．However,Bayeraspirinwasthemostwell-known,andformanyyears,itwasthemarketleader.
Bythe1950s,newpainkillerswereonthemarket．Aspirinwasnolongertheonlywaytotreatpainandreducefever．Bayerandothercompanieslookedforotherdrugstomake.
However,inthe1970stheygotasurprise．Doctorsnoticedthatpatientswhoweretakingaspirinhadfewerheartattacksthanotherpeople．ABritishresearchernamedJohnVanefoundthereasonaspirinhelpedtopreventheartattacks．In1982,hewontheNobelprizeforhisresearch．Doctorsstartedtotellsomeoftheirpatientstotakeaspirineverydaytopreventheartattacks．Ithasmadelifebetterforthemanypeoplewhotakeit．IthasalsomadealotofmoneyforcompanieslikeBayerthatproduceandsellit!
Whydidn'ttheFrenchscientistcontinuetomakethemedicinethatstoppedpain? A．Itdidn'tworkwell.
B．Itwashardtomake.
C．Ithurtthestomach.
D．Itwasnotcost-effective.
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答案解析：