The amount of dissolved calcium and magnesium, which increases the mineral content within water, determines the water's level of:

The correct answer is hardness, as it refers to the concentration of dissolved minerals, specifically calcium and magnesium, in water. These minerals contribute to what is known as "hard" water. When water contains higher levels of calcium and magnesium, it can lead to various practical implications, like scaling in pipes and appliances, and can affect soap and detergent effectiveness, making it harder for them to create suds. The measurement of water hardness is important for various applications, including residential use, industrial processes, and aquaculture, influencing not only those aspects but also water treatment and quality assessments.

Softness, on the other hand, refers to water that has low concentrations of these minerals, which is the opposite of hardness. Purity generally refers to the absence of contaminants and impurities in water. Contamination applies to the introduction of harmful substances or pollutants that compromise water quality, which does not specifically relate to the mineral content. Thus, hardness is the correct term to describe the water's level influenced by the presence of dissolved calcium and magnesium.