Concept:Marketing boards are established mainly to protect cash crop farmers from sudden price changes in export markets.
Explanation:Cash crop prices often rise and fall sharply in international markets.
This makes the income of farmers unstable from one season to another.
Marketing boards step in to buy produce at fixed or controlled prices.
This helps to reduce the effect of violent price fluctuations.
As a result, farmers receive a more regular and assured income over time.
Thus, the primary aim is not revenue collection, training, or warehousing alone.
Those functions may exist, but they are not the main objective.
The central purpose is to cushion farmers against unstable export prices and keep their earnings steady.
Answer:C. stabilize the incomes of cash crop farmers