Concept:Farmers' incomes become unstable when factors beyond their control or poor planning cause large swings in earnings.
Explanation:Poor storage facilities cause post-harvest losses, so farmers sell less and earn less.
Adverse weather conditions can destroy crops or sharply reduce yields.
A recession in the world economy lowers demand for farm exports, forcing prices and incomes down.
However, depending on too many crops actually spreads risk, because different crops may fail or sell at different times.
If a farmer depends on only one crop, income becomes very unstable.
Thus, dependence on too many crops is not a reason for farmers' unstable incomes.
Answer:A. Dependence on too many crops.