**Core Concept**
The defluoridation process is a method used to remove excess fluoride from drinking water, which is essential to prevent health problems such as fluorosis. The **National Environmental Engineering Research Institute (NEERI)** has developed a technique for this purpose.

**Why the Correct Answer is Right**
The correct answer is related to the specific technique developed by NEERI for defluoridation. Although the exact answer choice is not provided, the process typically involves the use of **chemical precipitation** or **adsorption** methods to remove fluoride ions from water.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it does not correspond to the NEERI-developed method.
**Option B:** Similarly, this option does not match the known defluoridation technique.
**Option C:** This choice is also incorrect as it is not associated with the NEERI method.
**Option D:** Without the correct answer provided, we cannot directly address why the other options are incorrect, but typically, the correct method would be specifically named and recognized.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that excessive fluoride consumption can lead to **dental fluorosis** and **skeletal fluorosis**, making defluoridation of drinking water an important public health measure.

**Correct Answer:** Correct Answer: D. Nalgonda Technique