Concept:Marketing boards are government agencies that help farmers sell and distribute their output.
Explanation:The main functions of marketing boards in Nigeria include grading farm produce, fixing prices, and arranging the marketing of farm produce.
These boards are mainly concerned with local and export marketing, not with bringing foreign goods into the country.
Importation of farm produce is handled by agencies that control trade and customs policies.
Therefore, importing farm produce is not a function of marketing boards.
Answer:B. Importation of farm produce