Which statement best defines surveillance?

• A. A mission to obtain information about an adversary.
• B. A type of surveillance
• C. Systematic observation of aerospace, surface, or subsurface areas, places, persons, or things, by visual, aural, electronic, photographic, or other means (PASSIVE)
• D. A plan for decontaminating equipment

Answer: (C)

Surveillance is the ongoing, organized watching of spaces, assets, or people to gather information, using multiple methods—visual, auditory, electronic, photographic, or other means—without actively engaging the subject. This definition captures the key points: it's systematic and continuous, it covers a broad range of targets and environments, and it emphasizes passive data collection rather than active confrontation or manipulation. The other options either state only a purpose without describing how information is collected, are tautological or irrelevant, or refer to something unrelated like decontaminating equipment.