Which of the following is a common method for removing contaminants from water?

Using activated carbon is a common and effective method for removing contaminants from water due to its highly porous structure and large surface area, which enable it to adsorb a wide range of impurities. Activated carbon is particularly effective in removing organic compounds, chlorine, and certain heavy metals, making it a vital component in many water treatment systems. It works by attracting contaminants to its surface through physical and chemical interactions, thus purifying the water.

In contrast, while boiling water can kill pathogens, it does not remove chemical contaminants such as heavy metals or pesticides. Filtration through sand, while effective for larger particles and some types of sediment, does not have the specificity and adsorption capacity that activated carbon provides for a broader range of contaminants. Letting water sit undisturbed may allow some settling of particulates, but it will not remove dissolved contaminants or improve the water quality significantly. Therefore, activated carbon stands out as a versatile and efficient method for contaminant removal in various water treatment applications.