Fill in each of the blanks with one of the words given in the following list. (You can select the corresponding serial number, such as A, B, C……) A.services B.cloud C.marketing D.storage E.automated F.layer G.resource H.management I.software J.results K.develop L.platform M.application N.SaaS O.foundation P.serves The architecture of a cloud is developed at three layers: infrastructure, platform, and application. The infrastructure 1 is deployed first to support IaaS (Infrastructure as a Service) services. This layer serves as the 2 for building the platform layer of the cloud for supporting PaaS(Platform as a Service) 3 . In turn, the platform layer is a foundation for implementing the 4 layer for SaaS applications. The infrastructure layer is built with virtualized compute, 5 ,and network resources. The abstraction of these hardware 6 is meant to provide the flexibility demanded by users. Internally, virtualization realizes 7 provisioning of resources and optimizes the infrastructure management process. The 8 layer is for general-purpose and repeated usage of the collection of 9 resources. This layer provides users with an environment to 10 their applications, to test operation flows, and to monitor execution 11 and performance. In a way, the virtualized cloud platform 12 as a "system middleware (中间件)"between the infrastructure and application layers of the 13 . The application layer is formed with a collection of all needed software modules for 14 applications. Service applications in this layer include daily office 15 work. The application layer is also heavily used by enterprises in business 16 and sales, consumer relationship management, financial transactions, and supply chain management