Explanation
This answer is based on the knowledge area of project cost management, which involves planning, estimating, budgeting, managing, and controlling the project costs. Earned value (EV) is a tool that measures the actual work completed and the value of that work, compared to the planned work and the budget. By using EV, the project manager canmonitor the project performance and progress, and identify any variances or deviations from the baseline. The project manager can also use cost triggers and trend analyses to detect and respond to any potential issues or risks that may affect the project cost. References: (Project Management Professional (PMP) Reference Materials source and documents) A Guide to the Project Management Body of Knowledge (PMBOK Guide) - Seventh Edition, Chapter
7: Planning and Managing the Budget, Section 7.3: Managing the Budget, page 173.
The Standard for Project Management, Part 2: Value Delivery System, Section 2.3: Project Monitoring and Controlling, page 53.