If freshwater is added to a region, what happens to seawater density and salinity?

The density and salinity goes down.

Explanation:

Salt water is denser than pure water.  As fresh water is added to salt water the concentration of salt goes down.  Since salinity is the amount of salt in the water that would go down with the concentration.  This would also mean that the density goes down since there is less salt per unit of volume which makes it so that there is less mass per unit of volume.  The formula for density is d=m/v so as the mass goes down per unit of volume so does the density.

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b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.