## **Core Concept**
The National Family Health Survey (NFHS) is a large-scale, multi-round survey conducted in a representative sample of households throughout India. It provides valuable data on health and family welfare, as well as other socioeconomic indicators. The survey is crucial for policymakers to assess the progress of various health programs.

## **Why the Correct Answer is Right**
The NFHS is conducted every 5 years. This periodicity allows for the collection of data over time, enabling the assessment of trends, the evaluation of the impact of health interventions, and the identification of emerging health issues. The 5-year interval is long enough to capture significant changes in health indicators but not so long that it becomes difficult to implement corrective measures.

## **Why Each Wrong Option is Incorrect**
- **Option A:** NFHS is not conducted annually. Conducting such a comprehensive survey every year would be resource-intensive and may not provide significantly different data from one year to the next.
- **Option B:** While some health surveys or data collections might occur biennially (every 2 years), the NFHS is not one of them. Its scope and the resources required for its execution make a biennial schedule less feasible.
- **Option D:** Conducting NFHS every 10 years would be too infrequent to capture changes in health indicators and the impact of health policies and programs over time.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the NFHS provides critical data for monitoring the United Nations' Sustainable Development Goals (SDGs), especially those related to health. The survey's findings are instrumental in shaping India's health policies and programs.

## **Correct Answer:** . 5 years