Dry land farming in India is a type of agricultural practice that relies solely on rainfall for water supply, without the use of irrigation. It is practiced in regions with low rainfall, where water scarcity is a challenge. The correct answer to the question is option 4, which states that dry land farming in India is largely confined to areas with rainfall less than 75 cm.

Option 1, which states 100 cm, is not the correct answer because areas with 100 cm of rainfall would generally have enough water for farming and may not require dry land farming techniques.

Option 2, which states 85 cm, is not the correct answer because although this amount of rainfall is relatively low, it is still higher than the threshold for dry land farming.

Option 3, which states 80 cm, is not the correct answer because it is also higher than the threshold for dry land farming.

Therefore, dry land farming in India is mainly restricted to areas with rainfall less than 75 cm, as mentioned in option 4. This indicates that these regions face significant water scarcity, making dry land farming the most viable option for agricultural production.