Cloudcomputingisaphraseusedtodescribeavarietyofcomputingconceptsthatinvolvealargenumberofcomputers_()__throughareal-timecommunicationnetworksuchastheInternet.Inscience,cloudcomputingisa_()__fordistributedcomputingoveranetwork,andmeansthe_()_torunaprogramorapplicationonmanyconnectedcomputersatthesametime.Thearchitectureofacloudisdevelopedatthreelayers:infrastructure,platform,andapplication.Theinfrastructurelayerisbuiltwithvirtualizedcompute，storage，andnetworkresources.Theplatformlayerisforgeneral-purposeandrepeatedusageofthecollectionofsoftwareresources.TheapplicationlayerisformedwithacollectionofallneededsoftwaremodulesforSaaSapplications.Theinfrastructurelayerservesasthe_(请作答此空)__forbuildingtheplatformlayerofthecloud.Inturn,theplatformlayerisfoundationforimplementingthe_()__layerforSaaSapplication.
A.foundation
B.hardware
C.software
D.network
正确答案是B