The project manager should develop a rollback plan next after determining the appropriate maintenance
window in the operational infrastructure change process. A rollback plan is a contingency plan that describes
how to revert to the previous state of the system or infrastructure in case of a failure or disruption during the
change implementation. A rollback plan can help to minimize the impact and risk of the change and ensure
business continuity and stability.

A milestone chart is the best chart to use to show major accomplishments for key events, because it displays the important deliverables or outcomes of a project along a timeline12. A milestone chart can provide a high-level overview of the project progress and achievements, without showing the details of each task or activity34. A milestone chart can also help communicate the project status and expectations to the stakeholders, and identify any potential risks or delays that may affect the project completion56. References = CompTIA Project+ Certification Study Guide7, CompTIA Project+ Certification Exam Objectives8, What is a Milestone Chart?1, How to Create a Milestone Chart in Excel in 3 Steps2, Milestone Chart: The Easiest Way to Track Project Milestones3, How to Use Milestones in Project Management4

The BEST way to coordinate management of multiple related projects is to establish a program. A program is a group of related projects that are managed together to achieve specific strategic business objectives. References: CompTIA Project+ Study Guide Section 2.2.1 The organization should establish a program to coordinate management of multiple related projects. A program is a group of related projects, subprograms, and program activities that are managed in a coordinated way to obtain benefits and control not available from managing them individually. A program can help to align multiple projects with strategic goals, optimize resources and risks, and deliver value to stakeholders.

The project scope is the document that defines and describes the project objectives, deliverables, requirements, boundaries, assumptions, and constraints. It also includes the success criteria that should be fulfilled by the product or service to meet the stakeholder expectations and the business case. The success criteria are the measurable standards that indicate whether the project has achieved its intended results. The other options are not correct because:
A quality plan is the document that defines and describes the quality standards, policies, procedures, tools, and techniques that will be applied to the project to ensure that the deliverables meet the requirements and the success criteria.
Contract obligations are the terms and conditions that bind the parties involved in a contractual agreement, such as the project manager, the customer, the sponsor, and the vendor. Contract obligations specify the roles, responsibilities, deliverables, payments, and penalties of each party.
A work breakdown structure (WBS) is a graphical representation of the project scope that breaks down the deliverables into smaller and manageable components. A WBS shows the hierarchy and relationship of the project elements, but does not include the success criteria. References = CompTIA Project+ Study Guide: Exam PK0-005, 3rd Edition, Chapter 6: Planning Projects, Part 2 (Scope, Quality, and Risk), pages 175-179; CompTIA Project+ Certification Exam Objectives, Domain 2: Project Planning, Objective 2.1: Given a scenario, create a project charter and project management plan.

Archiving project documentation is an important process to ensure that the project information is stored, retrieved, and updated in a consistent and efficient manner1. It also helps to meet legal requirements, enable long-term analysis, and support new projects and team members1. If the documentation was not archived as per the PMO standards, it would be difficult for the current project manager to find the relevant documents and learn from the previous project. This would cause the current project manager to keep asking questions to the previous project manager, who may not have all the answers or may not be available. Therefore, the most likely cause of this situation is that the documentation was not archived as per the PMO standards. References = CompTIA Project+ Study Guide: Exam PK0-005, 3rd Edition, Chapter 14: Closing the Project, page 403; How to Archive a Completed Project: A Guide for PMOs, Introduction and Benefits sections.