Correct Option
The correct option is High population pressure on land.
Explanation
Intensive Subsistence Agriculture is the most prevalent form of farming in the densely populated regions of monsoon Asia. It is primarily driven by the need to feed a large population using limited arable land.
- High population pressure on land is correct: The defining characteristic of this system is high population pressure on land. Due to high population density and inheritance laws, landholdings are extremely small and fragmented. Farmers cultivate every available piece of land intensively to maximize yield per unit area.
- Mechanised harvesting is incorrect: This type of agriculture is labor-intensive. Most operations are carried out manually or with the help of draft animals. Mechanization is limited due to small plot sizes and the abundance of cheap labor.
- Pastoral mobility is incorrect: Pastoral mobility is a feature of Nomadic Herding, where communities move with livestock. Intensive subsistence agriculture is a settled form of cultivation.
- Absence of irrigation is incorrect: Paddy cultivation is water-intensive. While it relies on monsoon rains, irrigation is widely practiced to ensure water security and to enable double or triple cropping during dry seasons.
Key Takeaway: Intensive subsistence agriculture (paddy-based) is characterized by small landholdings, high labor input, heavy use of manure, and high productivity per unit of land, necessitated by high population density.