The two most abundant elements in ocean water, besides hydrogen and oxygen, are a) salt and sodium. b) salt and chlorine. c) sodium and calcium. d) sodium and chlorine.

This could be either c or d because technically, sodium ions and chloride ions are the most abundant, not sodium and chlorine, and there is also a significant amount of calcium in seawater. The answer you're looking for is most likely d but check with your teacher to be sure! (it is not A or B as salt is not an element, but rather a type of compound)