Where can official guidance on individual security clearances be found?

The correct answer is AFI 31-501, which pertains to individual security clearances. This Air Force Instruction provides comprehensive guidance on the processes, responsibilities, and criteria for granting, maintaining, and revoking security clearances for personnel within the Air Force. It covers the types of clearances, the investigation requirements, and the standards for eligibility, making it the authoritative reference for matters regarding security clearances.

AFI 31-301 and AFI 31-401 deal with different aspects of security management and information protection, focusing on physical security and personnel security policy, respectively. AFI 31-601 addresses operations security, which is essential for safeguarding sensitive operations but does not specifically cover individual security clearances like AFI 31-501 does.