在IS0定义的开放系统互连模型(OSl/RM模型)中，数据加密是______层的主要功能之一。

跨境电子商务较之传统外贸经营模式的优势有（）

简述网络调研的优势。

完型填空(本大题共10小题，每小题1分，共10分)从选项中选择一个最适合短文的选项，错选、多选或未选均无分。

Joggingisbecomingoneofthe___21___growingactivitiesinthenation.Morepeoplearestartingjogeachyear.This,however,isarecentoccurrence.Itwasnotlongago__22____joggerswereraresight.Somepeoplethoughtthattheylookedquitestrange.As__23____peoplebeganjoggingthesightofthembecamemorecommon.Therearemanyreasons___24___apersontotakeupjogging.First,itisagoodformofexercise.Thisis__25____itinvolvestheuseofmanypartsofthebody.Theexercisingoftheheartisofgreatbenefit.Thisisoneofthemostimportantpartsofthehumanbody.Iftheheartdoesnotgettheneededexercise,seriousproblemscanoccur.___26___reasonforjoggingisforenjoyment.___27___beinggoodforpeople,itcanalsobeverymuchfun.Partofthefunofjoggingcomesfromtheopportunityitprovidesformeetingotherpeoplewhoenjoyit.One___28___thatshouldbeconsidered___29___apersontakesupjoggingasaformofexerciseofenjoymentisthatitisnotforeveryone.Peopleshouldfirstcheck30theirdoctorsandbepreparedtofindanotherformofexerciseifjoggingisnotrecommended.

21.A.fastestB.quickestC.mostD.best

22.A.whenB.whileC.thatD.as

23.A.manyB.thoseC.moreD.the

24.A.ofB.withC.forD.in

25.A.thatB.whyC.reasonableD.because

26.A.AB.OtherC.TheotherD.Another

27.A.ExceptB.ExceptforC.BesidesD.Regardlessof

28.A.matterB.eventC.thingD.occurrences

29.A.ofB.thatC.whatD.when

30.A.outB.overC.onD.with

简述电子货币的主要功能。