In which of these phases is a customers network assessed to determine its system readiness？ Select exactly 1 answer（s） from the following：（）。

A.providing a step-by-step plan that details the installation and service-commission tasks required in order to create a controlled-implementation environment that emulates a customer network
B.assessing the ability of site facilities to accommodate proposed infrastructure changes
C.developing and executing proof-of-concept tests， validating high-level infrastructure design， and identifying any design enhancements
D.improving the network management system and the performance and functionality of infrastructure operations

A.plan
B.design
C.implement
D.prepare

A.an assessment of the preparedness of the customers existing system infrastructure to support a propose solution
B.a comprehensive design that has been customized based on the operations processes， network management processes， and tools of its system
C.an in-depth assessment of the operational environment required to support the operation of both the current and planned solutions
D.the optimal technologies for supporting its business requirements and objectives