Atabasiclevel,cloudcomputingissimplyameansofdeliveringITresourcesas().AlmostallITresourcescanbedeliveredasacloudservice:applications,computepower,storagecapacity,networking,programmingtools,evencommunicationservicesandcollaboration(请作答此空).Cloudcomputingbeganaslarge-scaleInternetserviceproviderssuchasGoogle,Amazon,andothersbuiltouttheirinfrastructure.Anarchitectureemerged:massivelyscaled,()distributedsystemresources,abstractedasvirtualITservicesandmanagedascontinuouslyconfigured,pooledresources.Inthisarchitecture,thedataismostlyresidenton()"somewhereontheInternet"andtheapplicationrunsonboththe"cloudservers"andtheuser'sbrowser.Bothcloudsandgridsarebuilttoscalehorizontallyveryefficiently.Botharebuilttowithstandfailuresof()elementsornodes.Botharechargedonaper-usebasis.Butwhilegridstypicallyprocessbatchjobs,withadefinedstartandendpoint,cloudservicescanbecontinuous.What'smore,cloudsexpandthetypesofresourcesavailable——filestorage,databases,andWebservices——andextendtheapplicabilitytoWebandenterpriseapplications.
A.computers B.disks C.machines D.tools正确答案D
