Explanation
A statement of work (SOW) is a narrative description of the work required for the project. It includes the project objectives, scope, deliverables, schedule, budget, quality standards, and acceptance criteria. It also defines the roles and responsibilities of the project team and the client, and the terms and conditions of the contract. A SOW is a formal document that establishes the agreement between the project provider and the project customer, and that guides the project execution and control12.
The other options are not correct. A. A contract work breakdown structure (CWBS) is a hierarchical decomposition of the contract deliverables into smaller and manageable components. It helps to define the scope, cost, and schedule of the contract, and to monitor and report the contract performance3. B. A work breakdown structure (WBS) is a hierarchical decomposition of the project work into smaller and manageable components. It helps to define the scope, cost, and schedule of the project, and to assign the work packages to the project team4. C. A contract statement of work (CSOW) is a document that describes the work to be performed by a contractor or a vendor under a contract. It is similar to a SOW, but it is more specific and detailed, and it is used for procurement purposes5. References:
What is a Statement of Work (SOW)? - Definition from WhatIs.com
Statement of Work: Definition & Examples - ProjectManager
Contract Work Breakdown Structure (CWBS) - AcqNotes
Work Breakdown Structure (WBS) - Project Management Institute
Contract Statement of Work (CSOW) - AcqNotes