【Transportationandcommunicationnetworksbringpeopletogether.Yetsometimespeoplethemselvescreatebarriers(障碍)totransportationandcommunication.Insomecountrieslawsstoppeoplefrommovingfreelyfromplacetoplac】

　　Transportationandcommunicationnetworksbringpeopletogether.Yetsometimespeoplethemselvescreatebarriers(障碍)totransportationandcommunication.Insomecountrieslawsstoppeoplefrommovingfreelyfromplacetoplace.Overthecenturiesmanygroupsofpeoplehavebeendeniedthefreedomtotravelbecauseoftheirracereligionornationality.IntheMiddleAgesforexampleJewswereoftenforbiddentomoveaboutfreelywithincertaincities.SouthAfrica'sgovernmentusedtorequireblackAfricanstocarrypasseswhentheytravelwithinthecountry.Somegovernmentsrequireallcitizenstocarryidentificationpapersandtoreporttogovernmentofficialswhenevertheymove.

　　Countriessetupcustomspostsattheirborders.Foreigntravellersmustgothroughacustomsinspectionbeforetheyareallowedtotravelinthecountry.Usuallytravellershavetocarryspecialpaperssuchaspassportsandvisas(签证).Somecountriesevenlimitthenumberofvisitorstotheircountryeachyear. Othersallowtouriststovisitonlycertainareasofthecountryortheymayrequirethattravellersbewithanofficialguideatalltimesduringtheirstay.

　　Manyofthosebarrierstotravelalsoactasbarrierstocommunication.

　　Whentwogovernmentsdisagreewitheachotheronimportantmatterstheyusuallydonotwanttheircitizenstoexchangenewsorideasfreely.Countriesoftentrytokeepmilitaryorindustrialinformationsecret.

　　Todaypeoplehavetheabilitytotraveltocommunicateandtotransportgoodsmorequicklyandeasilythaneverbefore.Naturalbarriersthatweredifficultordangeroustocrossahundredyearsagocannowbecrossedeasily.Thebarriersthatpeoplethemselvesmakearenotsoeasytoovercome.Butinspiteofallthedifferentkindsofbarrierspeoplecontinuetoenjoytravelandtheexchangeofgoodsandideas.

　　6.Theexamplesinparagraph2areusedtotellthereadersthat_______

　　A.peoplehavebeenallowedtotravelfreelywithinthecountry

　　B.peoplehavenotbeenpermittedtotravelfreelyforvariousreasons

　　C.travellershavetocarryspecialpaperssuchas　passportsandvisas

　　D.customspostsarenecessaryatthebordersof　thecountries

　　7.Somegovernmentslimitthefreedomofcommuni