**Core Concept**
The purification of highly polluted water on a large scale involves the use of physical, chemical, and biological processes to remove contaminants and produce safe drinking water. This process is crucial for public health and requires efficient and effective methods to handle large volumes of water.

**Why the Correct Answer is Right**
Reverse osmosis (RO) is a widely used method for water purification on a large scale. It involves forcing the water through a semipermeable membrane under pressure, allowing the removal of dissolved solids, bacteria, viruses, and other impurities. This process is effective for treating a wide range of contaminants, including heavy metals, pesticides, and other inorganic and organic pollutants. The semipermeable membrane acts as a barrier, allowing water molecules to pass through while retaining larger particles and contaminants.

**Why Each Wrong Option is Incorrect**
**Option A:** Distillation is a method of water purification that involves boiling the water and then collecting the condensed steam, which is free from many contaminants. However, it is not the most effective method for removing dissolved solids and other impurities, making it less suitable for highly polluted water.
**Option B:** Activated carbon filtration is a method that uses activated carbon to remove impurities and contaminants from water. While it is effective for removing chlorine, lead, and volatile organic compounds, it is not sufficient for removing bacteria, viruses, and other microorganisms that can cause waterborne diseases.
**Option C:** Coagulation and sedimentation is a method that involves adding chemicals to the water to remove suspended solids and other impurities. While it is effective for removing particulate matter, it is not sufficient for removing dissolved solids and other contaminants that can cause waterborne diseases.

**Clinical Pearl / High-Yield Fact**
It's essential to note that water purification methods should be chosen based on the type and level of contamination present in the water. Reverse osmosis is particularly effective for removing dissolved solids and other impurities, making it a popular choice for large-scale water purification.

**Correct Answer:** C. Coagulation and sedimentation.