Explanation:

- The World Happiness Index ranks countries based on factors such as GDP per capita, social support, life expectancy, freedom to make life choices, generosity, and perceptions of corruption.

- The rankings reflect the subjective well-being of the population in different countries.

- For the year 2021, India was ranked 139 out of 149 countries in the World Happiness Report.

- India's placement indicates challenges in areas like health, economic stability, and social structures compared to other countries.

Correct Answer: Option 4, 139