The SOW (statement of work) is a document that defines the scope, deliverables, schedule, and resources of a project. It is a contractual agreement between the buyer and the seller that should be changed first when there are approved changes to the product. Changing the SOW will ensure that the project expectations and requirements are updated and aligned with the customer's requests. The other options are not documents that need to be changed first, but rather metrics or tools that can be used to measure or manage the project. Reference = CompTIA Project+ PK0-005 Certification Study Guide, Chapter 3: Initiating Projects; CompTIA Project+ Certification Exam Objectives, Domain 2: Project Planning, Objective 2.1: Develop a project scope document.