**Core Concept**
The question is testing the knowledge of a national-level system that provides reliable estimates of fertility and mortality. This system is crucial for public health planning, policy-making, and research. The correct answer is a vital source of demographic data in India.

**Why the Correct Answer is Right**
The correct answer is the Sample Registration System (SRS), which is a large-scale demographic survey conducted by the Office of the Registrar General and Census Commissioner of India. The SRS uses a dual-record system, where both continuous enumeration and periodic surveys are conducted to estimate fertility and mortality rates at the national and state levels. This dual-record system helps to improve the accuracy and reliability of the estimates. The SRS has been providing valuable data on fertility and mortality rates in India since 1969.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the National Family Health Survey (NFHS) is a large-scale survey conducted by the Ministry of Health and Family Welfare, but it does not provide annual estimates of fertility and mortality rates.

**Option B:** This option is incorrect because the Census of India is conducted every 10 years and provides a snapshot of the population at a particular point in time, but it does not provide annual estimates of fertility and mortality rates.

**Option C:** This option is incorrect because the National Health Profile (NHP) is a publication that provides a comprehensive overview of the health status of the population, but it does not provide annual estimates of fertility and mortality rates.

**Clinical Pearl / High-Yield Fact**
The Sample Registration System (SRS) is an essential source of demographic data in India, and its estimates of fertility and mortality rates are widely used by researchers, policymakers, and planners.

**Correct Answer: C. Sample Registration System (SRS)**