Final answer:
The Water Quality Index (WQI) developed by the National Sanitation Foundation (NSF) takes into account 9 different factors when determining water quality. Correct option is A.
Step-by-step explanation:
The Water Quality Index (WQI) developed by the National Sanitation Foundation (NSF) takes into account 9 different factors when determining water quality. These factors include temperature, pH, dissolved oxygen, turbidity, total suspended solids, biochemical oxygen demand, nitrate, phosphate, and fecal coliform. Each factor is assigned a weighted value based on its importance, and the overall index is calculated by combining the weighted values of all the factors.