Operational security (OPSEC) is a process that prevents sensitive information from getting into the wrong hands by viewing operations from the perspective of an adversary1. Facility access is a form of OPSEC that controls who can enter and exit a physical location where sensitive data or equipment is stored or processed. Facility access can include measures such as locks, alarms, badges, biometrics, guards, and cameras. The other options are not correct because:
Mobile device compliance is a policy that ensures that mobile devices used by employees or contractors meet certain security standards and requirements, such as encryption, password protection, antivirus, and remote wipe. Mobile device compliance is not a form of OPSEC, but rather a form of data security or device management.
Background screening is a process that checks the criminal, financial, and employment history of a potential employee or contractor before hiring them. Background screening is not a form of OPSEC, but rather a form of human resource management or risk mitigation.
Multifactor authentication is a method that requires users to provide two or more pieces of evidence to verify their identity before accessing a system or service, such as a password, a code, a token, or a biometric. Multifactor authentication is not a form of OPSEC, but rather a form of access control or identity management. Reference = CompTIA Project+ Study Guide: Exam PK0-005, 3rd Edition, Chapter 10: Executing and Closing Projects, page 314; CompTIA Project+ Certification Exam Objectives, Domain 3: Project Execution, Objective 3.2: Given a scenario, execute and monitor project tasks using traditional methodologies; What is Operational Security? The Five-Step Process, Best Practices, and More

This answer is based on the best practice of choosing a project management methodology that suits the project characteristics and environment12. Scrum is an agile framework that is designed to handle complex and uncertain projects with frequent changes and tight deadlines34. Scrum involves a small, cross-functional team that works in short iterations called sprints, delivering incremental and potentially shippable products at the end of each sprint5. Scrum also allows for continuous feedback and improvement through daily stand-up meetings, sprint reviews, and retrospectives6. Scrum is suitable for this project because it can accommodate the high uncertainty, the risk of requirement changes, and the tight deadlines, while also enabling the two developers to collaborate effectively and deliver value to the customer. Reference = CompTIA Project+ Certification Study Guide7, CompTIA Project+ Certification Exam Objectives8, Project Management Methodologies Comparison (11 PM Methods)6, Project Management Methodologies: 12 Best Frameworks [2023]7, What is Scrum?5, Scrum Methodology: The Ultimate Guide6

When a critical ERP system upgrade encounters a validation issue and is at risk of exceeding the allotted downtime, the project manager should begin executing the rollback plan. This action is taken to ensure that the system can be restored to its previous state without exceeding the downtime limit, thus minimizing the impact on the business operations.

This answer is based on the best practice of conflict resolution in project management, which is to use a collaborative or problem-solving approach that seeks a win-win outcome for all parties involved12. By facilitating a meeting, the project manager can help the team members communicate effectively, understand each other's perspectives, and find a mutually acceptable solution that meets the project requirements. This way, the project manager can also maintain team morale and cohesion, and avoid imposing a decision that may cause resentment or dissatisfaction among the team members3. Reference = CompTIA Project+ Certification Study Guide4, CompTIA Project+ Certification Exam Objectives5, How Do You Handle Conflict in Project Management?1, 7 Strategies for Conflict Resolution in Project Management2, The Conflict Resolution Skills Every Project Manager Needs3

A project manager who makes a company-wide announcement about the successful completion of a project and thanks team members is doing the following:
Celebrating the team's hard work: This is the correct answer, as the project manager is acknowledging the efforts and contributions of the team members and showing appreciation and recognition for their performance12.
Bringing attention to the project sponsor: This is not the correct answer, as the project manager is not highlighting the role or involvement of the project sponsor, who is the person who provides the resources and authority for the project.
Sharing lessons learned: This is not the correct answer, as the project manager is not discussing the successes, challenges, or best practices of the project, which are part of the lessons learned process.
Collecting feedback: This is not the correct answer, as the project manager is not soliciting any input or opinions from the team members or other stakeholders, which are part of the feedback process.