Security allegations on a person should be proved or disproved through which of the following personnel security investigations?

The appropriate personnel security investigation for proving or disproving security allegations is a Special investigation inquiry. This type of inquiry is specifically tailored to address serious allegations that may threaten national security or compromise sensitive information.

Special investigations are conducted when there are credible allegations, unusual circumstances, or specific threats that require a more thorough review than a standard background check or typical investigation. This inquiry often involves extensive interviews, record checks, and deeper inquiries into a person's past, character, and associations to assess their trustworthiness and reliability.

In contrast, a background check generally involves verifying an individual's identity, employment history, and criminal background. A standard investigation inquiry focuses on gathering routine information about a person's history and character but may not delve as deeply into serious allegations. A general investigation inquiry would also be more limited in scope and not specifically geared to address allegations that could impact security directly.

Thus, the Special investigation inquiry is uniquely equipped to handle the complexity and seriousness of security allegations, making it the correct choice for this matter.