## Core Concept
The Chadah Committee, established in 1969, played a pivotal role in shaping India's healthcare workforce policies. One of its significant recommendations was regarding the optimal population size that a Basic Health Worker (BHW) should serve, aiming to ensure accessible primary healthcare.

## Why the Correct Answer is Right
The Chadah Committee recommended that there should be 1 Basic Health Worker per 1,000 population in hilly, tribal, or backward areas, and 1 per 5,000 population in plain areas. However, the most universally applicable and remembered guideline from these recommendations is having 1 Basic Health Worker per 5,000 population.

## Why Each Wrong Option is Incorrect
- **Option A:** 1,000 population - This is indeed a recommendation but specifically for hilly, tribal, or backward areas, not the general or plain areas.
- **Option B:** 10,000 population - This is not in line with the Chadah Committee's recommendations.
- **Option D:** 20,000 population - Similarly, this does not align with the committee's suggested ratios.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the Chadah Committee's recommendations were instrumental in guiding India's approach to primary healthcare. Specifically, for plain areas, the guideline of 1 Basic Health Worker per 5,000 population is a crucial piece of information for any examination on healthcare planning and policy.

## Correct Answer: B. 5,000.