Explanation:

The limitations of national income estimation in India include:

1. Output of non-monetized sector: The national income estimation often does not capture the full output of the non-monetized or informal sector, which is a significant part of the economy, especially in developing countries.

2. Non-availability of data about income of small producers or household enterprises: Gathering accurate data about the income of small producers or household enterprises can be challenging, leading to underestimation of the true economic activity.

3. Unreported legal income: National income estimation may not fully account for unreported legal income, which includes income that is earned but not disclosed to tax authorities or other regulatory bodies.

4. Inflation: Inflation can distort the real value of output and income. While nominal GDP measures the total value of goods and services produced at current prices, it does not account for changes in the price level. Adjusting for inflation is necessary to obtain a more accurate measure of real economic growth.

So, all four statements are correct.