二、求函教 Demand function 需求曲线:表示商品价格与需求量之间关系的曲线。 Demand curve: a graph(曲线图) showing the relationship between the price of a good and the quantity of the good demanded over a given time period需求曲线：表示商品价格与需求量之间关系的曲线。 Demand curve: a graph (曲线图)showing the relationship between the price of a good and the quantity of the good demanded over a given time period. 二、需求函数 Demand function