The correct answer is A because the primary distinction between a Memorandum of Understanding (MOU) and a Statement of Work (SOW) lies in their legal enforceability and purpose. In the Security+ SY0-701 governance and third-party risk management context, an MOU is generally a formal but nonbinding agreement that outlines mutual expectations, responsibilities, and cooperation between parties. It establishes intent and alignment but typically does not impose enforceable obligations or penalties if terms are not met.

An SOW, on the other hand, is legally binding and serves as a contractual document that defines specific deliverables, timelines, performance metrics, and acceptance criteria. The SY0-701 study guide emphasizes that SOWs are critical in vendor and service provider relationships because they clearly define what work will be performed, how success is measured, and what happens if requirements are not met. This makes the SOW enforceable in legal and regulatory contexts, especially when dealing with sensitive systems or data.

Option B is incorrect because both MOUs and SOWs can identify engagement participants, but this is not their defining difference. Option C is incorrect because both documents typically require agreement from all involved parties, and signature requirements vary by organization and jurisdiction. Option D is incorrect because it reverses the actual level of detail: MOUs are high-level and conceptual, while SOWs are detailed and task-specific.

In security programs, MOUs are often used for cooperative arrangements, such as information sharing between organizations or government entities. SOWs are used when accountability, compliance, and measurable outcomes are required. Understanding this distinction is essential for managing third-party risk, enforcing security requirements, and maintaining compliance with Security+ SY0-701 governance objectives.