Expert A pointed out that China's domestic coal market structure has already exceeded supply. It proposed: "Either limit production or protect prices or reduce prices. ". If B insists on his opinion, which one can conclude that B must logically agree? ['Limit production to insure prices without reducing prices.', 'If neither limiting production nor insuring prices is possible, you must reduce both production and prices.', 'Reduce both production and prices.', 'Cut prices without reducing production to protect prices.']