Correct Answer: AThe first step in incorporating the Software Development Life Cycle (SDLC) for a startup software company, particularly with an emphasis on quality assurance and release processes, is to define security requirements. Security requirements are foundational elements that dictate the security-related functionalities and constraints the software must adhere to. By establishing these requirements at the outset, all subsequent stages of the SDLC will have clear guidelines on necessary security measures, ensuring that secure coding practices, code signing, and application vetting are effectively aligned with these requirements. Without defining security requirements first, secure coding standards lack a defined goal to meet, thereby making security requirements the most logical initial step.