Cloudcomputingisaphraseusedtodescribeavarietyofcomputingconceptsthatinvolvealargenumberofcomputers__请作答此空__throughareal-timecommunicationnetworksuchastheInternet.Inscience,cloudcomputingisa___72___fordistributedcomputingoveranetwork,andmeansthe___73___torunaprogramorapplicationonmanyconnectedcomputersatthesametime. Thearchitectureofacloudisdevelopedatthreelayers:infrastructure,platform,andapplication.Theinfrastucturelayerisbuiltwithvirtualizedcomputestorageandnetworkresources.Theplatformlay-erisforgeneral-purposeandrepeatedusageofthecollectionofsoftwareresources.TheapplicationlayerisformedwithacollectionofallneededsoftwaremodulesforSaaSapplications.Theinfrastucturelayerservesasthe___74___forbuildingtheplatformlayerofthecloud.Inturn,theplatformlayerisfounda-tionforimplementingthe___75___layerforSaaSapplication.
A.connected B.implemented C.optimized D.virtualized正确答案A
