单项选择题

PassageThree Questions31to35arebasedonthefollowingpassage. Trademarks（商标）identifyanddistinguishtheproductsofonebusinessfirmfromthoseofanother.Itmayincludeaword，asentence，aname，asymbol，apicture，oranycombinationofthese.Trademarksmustbeattacheddirectlytotheproduct.Manytrademarkscontainthenameoftheownerofthebusiness.Butmanufacturersoftenusesomewordtodescribethequalitiesoftheproduct，ormakeupaword.Thespokenpartofatrademarkiscalledthebrandname. Trademarksprovideasimplewayforpeopletodeterminewhoisresponsibleforaparticularitem.Theyalsohelppeopleidentifythebrandstheylikedinthepastsotheymaypurchasethemagain.Manufacturersusetrademarkstopromotethesaleoftheirgoods. Servicemarksalsoidentifygoodsandservices.Theydonothavetobeattachedtoaproduct.Companiesthatprovideservicestothepublic，suchastransportationcompanies，usethesemarkstoadvertisetheirservices.Forexample，abluesignwithabell，thesymboloftheAmericanTelephoneandTelegraphCompany，tellseverypasser-bythatapublictelephoneisavailableforuse. Lawstoprotecttherightsofthetrademarkownerweredevelopedintheearly1800’s.Mostcountriesnowprovideforregulationandregistrationoftrademarks.Animportantprotectionfortrademarkrightsisfederal（联邦的）registration.In1905，theU.S.Congresspassedthefirstfederallawontrademarkregistrationtobeheldconstitutional. Welearnfromthesecondparagraphthattrademarksareusefulinthat___________.