Which of the following is true about the demand curve?
选项：

A: A demand curve indicates the drop in the average per-unit production cost that comes with accumulated production experience.
B: A demand curve indicates the cost per unit of output in the long run.
C: A demand curve indicates the cost per unit of output in the short run.
D: In a monopoly, the demand curve does not indicate the total market demand resulting from different prices.
E: A demand curve shows the number of units the market will buy in a given time period at different prices that might be charged.