The correct option is (c).
Explanation
Salinity refers to the total content of dissolved salts in seawater. It is a critical property that influences the density, freezing point, and circulation of ocean waters.Statement 1 is Correct: Salinity is scientifically defined as the total amount of solid material (salts) in grams contained in one kilogram (1000 grams) of seawater. It is conventionally expressed as parts per thousand (ppt or ‰).
Statement 2 is Incorrect: The average salinity of the open ocean is approximately 35 parts per thousand (35‰). While salinity varies spatially-being higher in regions of high evaporation (e.g., the Red Sea at ~41‰) and lower in areas with significant freshwater influx-an average of 45‰ is excessively high for the global ocean.
Statement 3 is Correct: Seawater contains a variety of dissolved salts. Sodium chloride (NaCl) is the most abundant, constituting approximately 77.8% of the total dissolved salts. Other major salts include magnesium chloride, magnesium sulphate, and calcium sulphate.
Key Takeaway: Ocean salinity averages 35‰ and is defined as the mass of salt per 1000g of water, with sodium chloride being the dominant constituent.