The correct answer is C. Sodium chloride.
Sodium chloride is the most abundant mineral found in seawater, comprising about 85% of all dissolved salts. It is also the main component of table salt.
Calcium carbonate is the second most abundant mineral in seawater, comprising about 10% of all dissolved salts. It is a major component of limestone and chalk.
Potassium chloride is the third most abundant mineral in seawater, comprising about 3% of all dissolved salts. It is a major component of fertilizers and batteries.
Magnesium sulphate is the fourth most abundant mineral in seawater, comprising about 2% of all dissolved salts. It is a major component of Epsom salts and is used in many industrial applications.
Other minerals found in seawater include calcium sulfate, magnesium chloride, sodium bicarbonate, and potassium bromide.