**Core Concept**
The Sample Registration System (SRS) is a continuous demographic survey conducted in India to estimate birth and death rates, fertility rates, and other demographic indicators. It involves a dual-record system, where an enumerator continuously enumerates births and deaths, and an independent survey is conducted by an investigator-supervisor to validate the enumerator's records.

**Why the Correct Answer is Right**
The SRS uses a dual-record system to ensure accuracy and reliability of demographic data. The enumerator records births and deaths on a daily basis, while the investigator-supervisor conducts a monthly or quarterly survey to validate the enumerator's records. This dual-record system helps to minimize errors and biases, providing a more accurate estimate of demographic indicators. The SRS is a continuous survey, which means it provides data on a regular basis, unlike other surveys that are conducted at intervals.

**Why Each Wrong Option is Incorrect**
**Option A:** Decadal Census Enumeration is a one-time exercise conducted every 10 years to enumerate the population, but it does not involve continuous enumeration of births and deaths.

**Option C:** Model Registration System is not a widely recognized system for demographic data collection in India.

**Option D:** National Family Health Survey (NFHS) is a survey conducted every 5-6 years to collect data on health and family welfare, but it does not involve continuous enumeration of births and deaths.

**Clinical Pearl / High-Yield Fact**
The Sample Registration System is an example of a dual-record system, which is a reliable method for collecting demographic data. This method can be applied to other areas of public health, such as disease surveillance, to improve the accuracy and reliability of data collection.

**Correct Answer Line**
✓ Correct Answer: B. Sample Registration System