Which solution contains the most electrolytes dissolved per unit of volume?

Sea water contains the most electrolytes dissolved per unit of volume compared to the other options. This is primarily due to its high concentration of salts, particularly sodium chloride, along with other minerals such as magnesium, calcium, and potassium. The salinity of sea water is significantly higher than that of freshwater sources like ponds and rivers, which contain fewer dissolved minerals and electrolytes.

Tap water may have some minerals added for health benefits, but it typically lacks the high concentration of electrolytes found in sea water. Freshwater, while containing essential ions, is also much less concentrated in electrolytes than the saline environment of the ocean. Pond water generally contains a mix of freshwater and organic materials, leading to lesser electrolyte concentrations compared to the ocean. This high salinity in sea water is what establishes it as the solution with the most dissolved electrolytes per unit of volume.