Concept:Bonded warehouses are licensed premises where imported goods are stored before customs duties are paid.Explanation:Goods kept in a bonded warehouse are under customs control.Their import duties have not yet been fully paid.The warehouse is therefore supervised by the customs and excise authorities.These authorities ensure that no goods leave until all duties are settled.Clearing agents, immigration officers, and postal authorities have no such supervision role.Answer:B. customs and excise authorities