Which definition best describes the implementation service component within the implement phase？ 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. installing， configuring， and integrating systems components based on an implementation plan developed in earlier phases
E. improving a customer’s infrastructure security system