Concept:Subsistence agriculture is small-scale farming aimed at feeding the farmer's family.
Explanation:In subsistence agriculture, the farmer produces just enough food for household needs.
Large machines, electricity, and heavy animal power are usually not affordable or necessary.
The farmer performs most tasks using physical effort, such as planting, weeding, and harvesting.
Therefore, human energy, or man power, is the main source of power on such farms.
Answer:D. man