The correct answer is: D. Mg
Magnesium is the most abundant metal in seawater, making up about 0.13% of the total mass. It is also the third most abundant element in the Earth’s crust, after oxygen and silicon. Magnesium is a light, strong metal that is used in a variety of applications, including alloys, batteries, and fertilizers.
Calcium is the second most abundant metal in seawater, making up about 0.04% of the total mass. It is also the fifth most abundant element in the Earth’s crust. Calcium is a major component of bones and teeth, and it is also used in a variety of other applications, including construction, agriculture, and pharmaceuticals.
Sodium is the third most abundant metal in seawater, making up about 0.02% of the total mass. It is also the sixth most abundant element in the Earth’s crust. Sodium is a major component of salt, and it is also used in a variety of other applications, including food processing, water treatment, and manufacturing.
Potassium is the fourth most abundant metal in seawater, making up about 0.01% of the total mass. It is also the seventh most abundant element in the Earth’s crust. Potassium is a major component of fertilizers, and it is also used in a variety of other applications, including batteries, pharmaceuticals, and food processing.