答案:A demand curve shows the number of units the market will buy in a given time period, at different prices that might be charged. Each price the company might charge will lead to a different level of demand. The relationship between the price charged and the resulting demand level is shown in the demand curve. In the normal case, demand and price are inversely related—that is, the higher the price, the lower the demand. Thus, the company would sell less if it raised its price from P1 to P2. In short, consumers with limited budgets probably will buy less of something if its price is too high. Understanding a brand's price-demand curve is crucial to good pricing decisions. Most companies try to measure their demand curves by estimating demand at different prices. The type of market makes a difference. In a monopoly, the demand curve shows the total market demand resulting from different prices. If the company faces competition, its demand at different prices will depend on whether competitors' prices stay constant or change with the company's own prices.