The dual-track system is an institutional arrangement adopted by China in transitioning from a planned economy to a market economy. It has been widely used in various economic fields. So far, the market for all industrial products and most agricultural products in China has been fully liberalized. Degrees still exist, which reflects the complexity and particularity of the reform of the food distribution system. Based on this text, the correct understanding of the "dual-track system" is:. ['The timing of the complete withdrawal of the dual-track system under a market economy is still immature.', 'During the planned economy period, the dual-track system was generally adopted for industrial products.', 'The opening of the agricultural product market is just around the corner.', 'The dual-track system of food markets restricts free trade in food.']