What is the most common salt found in ocean water?

A. potassium

B. calcium carbonate

C. magnesium

D. sodium chloride

I believe the correct answer from the choices listed above is option D. The most common salt found in ocean water would be sodium chloride. Seawater or ocean water contains many types of salt and the most abundant type of dissolved ions are sodium and chloride ions which when crystallized becomes NaCl.