Which manual outlines the operational aspects of recruiting?

The correct choice pertains to the manual that specifically addresses the operational aspects of recruiting. In the context of USAREC, UM 3 is established as the comprehensive guide that provides detailed procedures, techniques, and standards for the recruitment process. This manual is designed to assist recruiters by offering structured guidance on how to effectively engage and process potential recruits, ensuring that their methods align with the Army's recruitment objectives.

Other options may pertain to various military functions, but UM 3 is explicitly focused on recruiting operations, making it crucial for those involved in the recruitment process to refer to this manual for comprehensive operational guidance.