Which is NOT commonly considered a phase of the SDLC?

• A. Requisition phase
• B. Requirements analysis phase
• C. Concept development phase
• D. Testing phase

Answer: (C)

When studying how the SDLC is typically organized, you look for a sequence of well-defined stages that produce a usable system: planning and requirements analysis, design, development, testing, deployment, and ongoing maintenance. Concept development is more about exploring ideas and assessing feasibility before a project正式 kicks off, and it isn’t usually named as a formal SDLC phase in most models. Because of that, it isn’t commonly treated as a standard phase within the SDLC, making it the best answer. The other options align more directly with recognized SDLC activities: requirements analysis and testing are core phases, and requisition-type activities often occur within planning or procurement parts of the lifecycle.