**Core Concept**
The Indian Public Health Standards (IPHS) guidelines aim to standardize the infrastructure and human resources required for providing primary healthcare services at various levels, including subcenters. The guidelines emphasize the importance of adequate female health workers to ensure accessible and culturally sensitive healthcare for women and children.

**Why the Correct Answer is Right**
According to the IPHS norms, the proposed number of female health workers at a subcenter is one. This is to ensure that women and children have access to healthcare services that are delivered by female health workers, particularly for reproductive and maternal healthcare. The presence of a female health worker at the subcenter is crucial for promoting institutional delivery, providing family planning services, and conducting antenatal and postnatal check-ups.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the IPHS guidelines specify a single female health worker at each subcenter.
**Option B:** This option is incorrect because the number of female health workers may vary depending on the population served by the subcenter, but the IPHS guidelines recommend a minimum of one.
**Option C:** This option is incorrect because the IPHS guidelines do not specify a specific number of female health workers based on the subcenter's catchment area.
**Option D:** This option is incorrect because the IPHS guidelines are specific about the staffing requirements for subcenters, and the number of female health workers is a critical component.

**Clinical Pearl / High-Yield Fact**
The IPHS guidelines aim to standardize healthcare services across the country, and the staffing requirements for subcenters are a critical aspect of this effort. Familiarity with the IPHS guidelines is essential for public health professionals and policymakers.

**Correct Answer:** C. One female health worker.