What are some warning signs of possible security threats?

The correct answer highlights several indicators that may point to potential security threats. Unusual behavior can include actions that are out of the ordinary for the setting, such as someone loitering around restricted areas without a clear purpose or behaving nervously. Unauthorized access attempts involve individuals trying to enter secure zones without proper identification or clearance, which is a direct security risk. Rapid changes in the environment, such as unexpected alterations in security protocols or an influx of unfamiliar individuals, can also signal potential threats as these changes may reflect an underlying issue.

This option effectively combines various elements that, when observed together, can create a clearer picture of an impending security concern. Recognizing these signs allows for faster and more informed responses to possible threats, thereby enhancing overall safety and security onboard.