Explanation:

- The National Sample Survey (NSS) of India is a government-run survey program that started to gather demographic and socio-economic data.

- It provides crucial information on various aspects like population, birth and death statistics, internal migration, and more.

- The survey also covers data on employment, unemployment, health, and housing conditions, which is valuable for policy formulation.

- Option 1: 1955 - It is not the correct start year for the National Sample Survey.

- Option 2: 1952 - Also not the right year when the survey began.

- Option 3: 1951 - Incorrect timing as well.

- Option 4: 1950 - The correct year when the National Sample Survey was initiated.

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