Ocean water has a salinity of 35 parts per thousand. Fresh water has a salinity of less than 0.5 parts per thousand. What can you conclude from this information? A. Ocean water is rich in salt minerals. B. The salinity of ocean water varies considerably. C. Fresh water contains no salt at all. D. Most of the salt in ocean water is magnesium.

A is correct since there is an abundance of salt minerals/salt in the ocean water that causes to be quite considerably salty.

A salinity of 35 parts per thousands is 3.5% of a thousand. That means for every litre of of seawater, there is 35 grams of salt most dissolved in it.

Also, the salinity of the ocean does stagnate around 3.5% but in some parts of the world, it depends on where it is located, and the salinity might be higher and others parts may be much lower. Therefore B is incorrect as it doesn't vary considerably.

Freshwater does contain a very very tiny amount of salt and that indicates that freshwater containing no salt at all is a false statement.

Lastly, most of the salt in ocean water is not magnesium since most of salt in ocean water is sodium but magnesium is the second most commonly found cation in oceans. Freshwater contains very little magnesium while the oceanic marine bodies do.

For example: rivers contain upwards of 4ppm of magnesium while marine algae can contain from between 6,000 to 20,000 ppm of magnesium.