What are the three types of alarms and signals used for NBC contamination warnings?

The correct response identifies the three types of alarms and signals used for Nuclear, Biological, and Chemical (NBC) contamination warnings as audible, automatic, and visual. This classification is crucial in ensuring that military personnel can recognize and respond to potential threats efficiently.

Audible signals are sound-based warnings such as sirens or alarms that can reach personnel over considerable distances, ensuring that everyone in the area is alerted to the danger. Automatic signals refer to systems that activate without human intervention, often relying on sensors to detect contamination and trigger warnings. Visual signals, such as colored flags or lights, provide immediate, discernible alerts to individuals regardless of whether they can hear audible signals. This triad of alert types is essential for a well-rounded approach to NBC readiness, ensuring that warnings can be communicated effectively across varied environments and circumstances.

The options focused on manual, digital, or mechanical systems do not encompass the comprehensive nature of how alerts are delivered during NBC incidents, hence why the other responses do not fit the established protocols for contamination warnings. Understanding the correct types of alarms and signals is vital for maintaining safety and readiness in operations.