## Core Concept
The question pertains to the classification and coverage of healthcare services based on population size. In healthcare organization and planning, different levels of healthcare facilities are designated to serve specific population sizes, ensuring efficient distribution of resources and access to care.

## Why the Correct Answer is Right
The correct answer, **.**, corresponds to the definition that a subcentre is the most peripheral and first contact point between the primary healthcare system and the community. It covers a population of 1000 in hilly, tribal, or backward areas and 5000 in plain areas. However, given the options and common classification:
- Subcentre: 5,000 (plain areas) or 3,000 (hilly, tribal, or backward areas)
- Primary Health Centre (PHC): 30,000 (hilly, tribal areas) or 40,000 (plain areas)
- Community Health Centre (CHC): 80,000 to 120,000

## Why Each Wrong Option is Incorrect
- **Option A:** This option does not correspond with the typical population coverage for basic healthcare units.
- **Option B:** Similarly, this does not match known population coverage for healthcare facilities.
- **Option D:** This option also does not align with standard population coverage numbers for different types of healthcare facilities.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the subcentre is the first contact point between the primary healthcare system and the community, typically covering 5000 population in plain areas and 3000 in hilly, tribal, or backward areas.

## Correct Answer: C.