The stage where users have the greatest involvement is investigation. Option D
In the Software Development Life Cycle (SDLC), users typically have the most involvement during the stages of investigation and design.
During the investigation phase, users are extensively engaged in identifying and specifying the requirements. This stage involves gathering information, analyzing business needs, and understanding user requirements, ensuring that the developed software aligns with user expectations.
Subsequently, in the design phase, users continue their involvement by collaborating with developers and designers to create the software's structure, functionalities, and user interface, ensuring that it meets their needs and preferences.