What happens when water’s salinity increases? mass decreases. freezing point decreases. buoyancy of objects decreases. the amount of dissolved minerals decreases.

That would be B.

Increase in salinity causes decrease in freezing temperature and increase in boiling temperature of water. That’s why they dump salt on snow or add it to water while cooking:)

Freezing point decreases.

Explanation:

Decreasing of freezing point is a colligative property, which depends on the number of solute particles in the solution. As the number of solute particle increases the freezing point decreases.  

Salt water has a lower freezing point than plain water.  

Salt water does not have a different mass than plain water. Option A is incorrect.

Salt water does not affect the buoyancy or the mineral dissolved in it.  Both option C and D are incorrect

The more water there is, the lower the salinity levels. The lower the water there is, the higher the salinity levels. The higher the salinity levels, the denser the water.

The right answer is Freezing point decreases.

The explanation of the lowering of the freezing point of water is as follows: it is an entropic phenomenon, that is to say geometric. By interposing between the water molecules, the salt dilutes the water.

Let's see this in more detail: when the ice is in equilibrium in the water, there are in fact constantly ice molecules escaping into the water and, in equal numbers, molecules of water that come to settle on the ice. The salt ions dilute the water and cause the water molecules to be more distant (and therefore the water will not turn into ice).