The correct option is High labour input per unit area.
Explanation
Farming systems are distinguished by the intensity of inputs (labor, capital, machinery) relative to the land area and the primary purpose of production. Intensive subsistence farming is prevalent in densely populated regions (e.g., Monsoon Asia), while extensive commercial agriculture is practiced in sparsely populated regions with vast land resources (e.g., North American Prairies, Pampas of Argentina).
Analysis of Characteristics:
- High labour input per unit area is correct: Intensive subsistence farming is characterized by high population pressure on land. To maximize output from small, fragmented holdings, there is a high input of manual labour per unit area. Farmers use every available piece of land and rely heavily on family labor and animal power rather than machinery.
- Heavy dependence on machinery is incorrect: Heavy dependence on machinery is a defining characteristic of extensive commercial agriculture. In these systems, labor is scarce and expensive, necessitating the use of large machines (combine harvesters, tractors) to manage vast tracts of land.
- Very large land holdings is incorrect: Very large land holdings are typical of extensive commercial agriculture. In contrast, intensive subsistence farming is associated with very small and fragmented land holdings due to high population density and inheritance laws.
- Dominance of export-oriented crops is incorrect: Dominance of export-oriented crops is a feature of commercial agriculture. Subsistence farming is primarily aimed at meeting the food requirements of the farmer's family, with only the surplus being sold in local markets.
Key Takeaway:
The fundamental differentiator is that intensive subsistence farming relies on high labor input on small landholdings to maximize yield per acre, whereas extensive commercial agriculture relies on mechanization on large landholdings to maximize yield per worker.