Which statement defines mark in CBRN reconnaissance?

• A. Use of visual or other indicators to warn others of a hazard.
• B. To record data during a survey.
• C. To calibrate detectors.
• D. To analyze samples in a lab.

Answer: (A)

In CBRN reconnaissance, marking is about signaling danger so others know to avoid or proceed with caution. The best description is using visual or other indicators to warn people about a hazard. This is essential in the field because it communicates risk quickly and clearly, helping to prevent exposure and guide safe movement through potentially contaminated areas.

The other tasks described—recording data during a survey, calibrating detectors, and analyzing samples in a lab—are separate activities: data collection, instrument maintenance, and lab work. They don’t convey the hazard to others in the environment, which is the core purpose of marking.