In CBRN reconnaissance, you first gather the situational picture by surveying the area to determine where hazards are and how they affect the terrain and routes. The next step is to mark the area, which communicates to all teammates and supporting units exactly where the hazards are and where safe paths or exclusion zones exist. This marking is crucial because it translates the initial information from the survey into visible, actionable guidance that protects personnel and sets the boundaries for subsequent work. Once the area is marked, teams can proceed to quantify contamination, validate findings, and report results with confidence, knowing the zone boundaries and hazard locations are clearly established. Quantifying or reporting before marking would either risk exposure or rely on uncommunicated, ambiguous information, so marking right after surveying is the logical next move.

In CBRN surveillance, the emphasis is on methods that actively monitor for chemical, biological, radiological, or nuclear threats using sensors or planned checks. Periodic surveillance fits because it involves checks at set intervals to detect contaminants or anomalies. Continuous surveillance fits because it relies on real-time or near real-time monitoring by sensors to catch changes as they happen. Area Array surveillance fits as well because it deploys a network of sensors across a defined area to detect signals indicating a threat. Geospatial mapping surveillance, however, is about plotting and analyzing spatial data to visualize where events are occurring or how they might spread; it supports understanding and decision-making but does not itself perform detection or ongoing monitoring of CBRN agents. Therefore, it is not considered a direct CBRN surveillance technique.

The key idea is the order and content of METT-TC used in reconnaissance planning. METT-TC stands for Mission, Enemy, Terrain and Weather, Time, Civil Considerations, and the plan follows that exact sequence. Start with the mission to anchor what you’re trying to accomplish, then assess the enemy to understand threats and capabilities, then evaluate the terrain and weather to know how the environment will affect movement, concealment, and opportunities, followed by the time factor to plan tempo and sequencing, and finally consider civil factors that can influence safety, information needs, and legitimacy. This order preserves the logical flow planners use to build a complete operational picture, ensuring no factor is considered out of place. Other options mix up these elements or place Civil Considerations earlier, which disrupts the standard decision-making sequence and can hide important interdependencies, like how civil factors might constrain timing or how terrain affects civilian access and safety.

Understanding immersion limits helps keep the device safe and functional in water. The specified maximums are one meter of immersion depth and a duration of 30 minutes. The choice that matches exactly those limits is the one that lists one meter for 30 minutes, making it the correct pick. The other options push beyond the allowed limits in at least one dimension—either deeper than one meter or staying submerged longer than 30 minutes (or both)—which is why they aren’t the correct specification.