Is ocean water a pure substance?

I think my answer for 'Is ocean water a pure substance?' is seawater is a mixture of many different substances. Some of these substances can be observed when the water in seawater evaporates and leaves behind salt. Water H2O is a pure substance a compound made of hydrogen and oxygen.
I hope my answer is correct.

The answer is accuracy

Well you can immediately rule out a and d because if a metal were to lose or gain protons, then it would become a different element all together. the answer here is b because the positive symbol with a number refers to how many electrons the metal can give away to become stable.