Final answer:
In the context of a SCIF, reporting a coworker's significant change in behavior is a true requirement. This is part of maintaining operational security and potentially preventing risks associated with insider threats.
Step-by-step explanation:
The question pertains to whether an individual should report observable changes in a coworker's behavior when working in a Sensitive Compartmented Information Facility (SCIF). Reporting such observations is typically a security requirement in environments dealing with classified information.
Vigilance in a SCIF is critical, and noticing changes in someone's behavior could potentially be linked to security risks. Therefore, you are required to report this information about Sydney if you notice they have become very unhappy or disgruntled is true. This is essential to maintaining operational security and protecting sensitive information. It is part of an employee's responsibility to report any behavior that might pose a risk.