New Mexico Water Operator Level 4 Practice Exam

Total dissolved solids measure the amount of substances that are dissolved in water, meaning they pass into solution and stay in the water rather than settling out or being filtered as a solid. These dissolved substances include both inorganic and organic components, such as minerals (calcium, magnesium, sodium, potassium), salts (chloride, sulfate, bicarbonate), trace metals, and various organic compounds. Because they exist in solution, they contribute to properties like electrical conductivity and taste, and they are typically reported in mg/L (or ppm).

So the best description is the sum of all dissolved inorganic and organic substances. The other options refer to solids that are not dissolved (total suspended solids), or to aspects like color, or to a subset of dissolved materials (minerals only), which do not capture the full definition of TDS.