The correct answer is D. chlorine, sodium, magnesium, calcium, potassium, sulphate.
Chlorine is the most abundant element in seawater, followed by sodium, magnesium, calcium, potassium, and sulphate. These six elements make up over 99% of the dissolved salts in seawater.
Chlorine is present in seawater as chloride ions, which are formed when chlorine atoms combine with hydrogen ions. Sodium is present in seawater as sodium ions, which are formed when sodium atoms combine with chloride ions. Magnesium is present in seawater as magnesium ions, which are formed when magnesium atoms combine with chloride ions. Calcium is present in seawater as calcium ions, which are formed when calcium atoms combine with chloride ions. Potassium is present in seawater as potassium ions, which are formed when potassium atoms combine with chloride ions. Sulphate is present in seawater as sulphate ions, which are formed when sulphur atoms combine with oxygen atoms.
The relative abundance of these elements in seawater is determined by a number of factors, including the Earth’s geology, the weathering of rocks, and the biological activity of organisms.