Concept:Marketing boards help stabilise farmers' income by regulating the purchase and pricing of agricultural produce.
Explanation:A marketing board is a government-established agency that oversees the buying and selling of certain farm commodities.
It buys produce from farmers at fixed minimum prices, especially when there is a surplus in the market.
This prevents a sudden fall in prices and guarantees farmers a steady income.
Local government authorities mainly provide administrative services, not price support.
Trade unions focus on workers' wages and conditions, not agricultural pricing.
Co-operative organisations help farmers in collective buying and selling but do not have the same regulatory power as marketing boards.
Therefore, marketing boards act as a stabilising force for farmers' earnings.
Answer:C. Marketing boards