Which type of indicators reflect military structural changes or threats?

The selection of OPSEC indicators as the correct answer is well-founded because Operations Security (OPSEC) indicators serve to identify and mitigate vulnerabilities related to the potential adversaries' ability to exploit information about military operations or organizational structures. These indicators are crucial as they help in assessing changes in military posture, structure, or emerging threats that could compromise mission security.

OPSEC indicators can include information leaks, unusual patterns in communication, or alterations in personnel deployments that point to strategic changes or imminent threats. By monitoring and analyzing these indicators, military personnel can anticipate and respond to potential risks, ensuring that operations remain covert and effective.

Logistics indicators primarily focus on the movement and availability of resources rather than directly indicating structural changes or threats. Operations indicators are more aligned with the execution of missions rather than reflecting changes in military structure. Communications indicators involve the transmission of information but do not necessarily convey threats related to structural modifications. Thus, OPSEC indicators stand out as the most relevant type when it comes to reflecting military structural changes or threats.