Includes primary, secondary, and tertiary treatment.

• A. Drinking water treatment
• B. Desalination
• C. Wastewater treatment
• D. Industrial wastewater management

Answer: (C)

The idea being tested is the standard sequence used to treat municipal wastewater: primary, secondary, and tertiary treatment. In a wastewater treatment plant, solids are first removed in primary treatment through settling; then the remaining organic matter is biologically degraded in secondary treatment; and finally, advanced polishing steps in tertiary treatment remove residual nutrients, pathogens, or specific contaminants to meet discharge or reuse goals. This multi-stage approach is characteristic of wastewater treatment processes.

That’s why wastewater treatment is the best fit. Drinking water treatment aims to make water safe to drink and, while it uses multiple steps, it’s not typically described with primary/secondary/tertiary terminology. Desalination focuses on removing salts from seawater or brackish water, not the layered removal of solids, organics, and nutrients. Industrial wastewater management is broader and context-specific, and the statement about including all three stages most closely aligns with municipal wastewater treatment.