Final answer:
The best explanation for the necessity of wastewater treatment in urban areas is that the water must be made fit for human use and to avoid environmental contamination. Wastewater treatment involves multiple stages including primary, secondary, and tertiary treatments to remove contaminants and pathogens.
Step-by-step explanation:
The statement that best explains why proper wastewater treatment is necessary for urban areas is: d) Water must be fit for human use or consumption. Urban areas generate large amounts of wastewater from various sources including domestic, industrial, and agricultural activities. This wastewater must undergo treatment to remove contaminants and reduce waterborne diseases before it is fit for reuse or release into the environment.
Wastewater Treatment Plants in urban areas are equipped with several stages, such as primary treatment for solid removal, secondary treatment for bacterial decomposition, and tertiary treatment for additional filtration and disinfection, to ensure that the water is clean enough for its intended use and does not harm the ecosystem.