Desalination Targets Salt in Seawater

Steps:

• Identify the purpose: Desalination purifies seawater by removing dissolved salts to make it safe for drinking.
• Recall seawater composition: Seawater contains high levels of salts, primarily sodium chloride (table salt).
• Understand the process: Methods like reverse osmosis or distillation separate water from these salts.
• Match to options: Select the primary salt removed, which is sodium chloride.

Why D is correct:

• Desalination specifically removes dissolved salts; sodium chloride is the main salt in seawater, comprising about 85% of its total salinity by definition of ocean chemistry.

Why the others are wrong:

• A: Detergent is a pollutant from household waste, not naturally in seawater or targeted by desalination.
• B: Fertiliser is an agricultural runoff contaminant, unrelated to seawater's natural salt content.
• C: Sewage is organic waste from human activity, addressed by wastewater treatment, not desalination.

Final answer: D