The quantity of oxygen that can be dissolved in water is directly related to what factor?

The correct answer is related to temperature and its impact on the solubility of gases in water. As the temperature of water increases, the ability of water to hold dissolved gases like oxygen decreases. This is because higher temperatures provide more energy to the molecules in the water, which allows gas molecules to escape more readily from the liquid phase into the atmosphere. Therefore, colder water can hold more dissolved oxygen, making temperature a crucial factor in determining the concentration of dissolved oxygen in aquatic environments.

While other factors such as salinity, pressure, and pH do affect dissolved oxygen levels, they do so in more complex ways. For example, increased salinity typically decreases dissolved oxygen solubility due to changes in the water's density and structure, while pressure can enhance solubility but is less commonly encountered at the surface level where most aquatic life exists. pH can influence biological processes that consume or produce oxygen, but it does not have a direct linear relationship with the amount of oxygen that water can hold. Therefore, temperature is the most direct factor affecting the solubility of oxygen in water.