* Abackdooris a deliberate vulnerability inserted into the code, often allowing unauthorized access. * Source code review (Option D)is the best way to detect malicious code before it is deployed to production. * SDLC training (Option A)is helpful but does not directly prevent the insertion of backdoors. * Dynamic analysis (Option B)detects vulnerabilities at runtime but may not always identify backdoors in code. * Debugging (Option C)is useful for troubleshooting but does not address security vulnerabilities. #Reference:CompTIA CySA+ CS0-003 Official Study Guide, Secure Software Development Practices.