Final answer:
The correct answer is D) Conventional treatment. Filtration is commonly referred to as conventional treatment and involves a series of steps to remove small particles from the water.
Step-by-step explanation:
The correct answer is D) Conventional treatment. Filtration, preceded by coagulation, flocculation, and sedimentation, is commonly referred to as conventional treatment. In this process, the water undergoes a series of steps including coagulation and flocculation to neutralize and bind the dirt and particles, sedimentation to settle the floc particles, and finally, filtration to remove small particles from the water. It is an effective method used in water treatment plants to ensure safe and clean drinking water.