Which is the best example of interaction between physical and human factors in population distribution?

Correct answer: Development of irrigation roads and markets in a fertile plain

Direct answer: Option A is correct. This option shows interaction between a physical factor and human factors. Fertile plains provide productive soil and relatively favourable land, while irrigation, roads, and markets are created or improved by people. Together they support farming, trade, jobs, transport, and dense settlement. Step by step: fertile land supports crops; irrigation supplies water; roads connect producers and consumers; markets encourage buying and selling; these activities provide livelihoods and attract people. Option A is therefore the best combined example. Option B is wrong because it gives only a natural difficulty and does not show human action. Option C is wrong because cold climate alone is only a physical factor, not an interaction. Option D is wrong because lack of transport alone states a human limitation but does not combine it with a physical opportunity or human development. Memory cue: physical conditions provide the base; human development changes how people use it.