**Core Concept**
The purification of water involves several processes to remove contaminants and make it safe for consumption. These processes include physical methods like filtration and sedimentation, as well as chemical methods such as disinfection and coagulation. Understanding the effectiveness and applications of each method is crucial for ensuring water quality.

**Why the Correct Answer is Right**
Without the specific details of each option, the general principle of water purification can be discussed. Typically, methods like chlorination are effective against a wide range of pathogens, including bacteria and viruses. However, the correct answer might involve a method that is less effective or has specific limitations, such as the inability to remove certain chemical contaminants.

**Why Each Wrong Option is Incorrect**
**Option A:** Might be incorrect if it describes a widely recognized and effective method of water purification.
**Option B:** Could be wrong if it outlines a necessary step in the water treatment process that is universally accepted.
**Option C:** Might be incorrect if it refers to a method that, while not the most effective, still contributes to the removal of certain contaminants.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that no single method of water purification is 100% effective against all types of contaminants, making a combination of methods necessary for comprehensive water treatment.

**Correct Answer:** D. Distillation is not always necessary for purification of drinking water.