A demand curve __ x is a willingness-and-ability -to-pay curve tells us that marginal benefit rises as the quantity purchased increases is a marginal cost curve shows us that the highest price that someone is willing to pay for a an additional unit of a good or service rises as the quantity increases

## Step 1<br />A demand curve is a graphical representation of the relationship between the price of a good or service and the quantity of that good or service that consumers are willing and able to purchase at each price. <br /><br />## Step 2<br />The demand curve is downward sloping, which means that as the price of a good or service increases, the quantity demanded decreases, and vice versa. This is because as the price of a good or service increases, consumers are less willing or able to pay for it, leading to a decrease in quantity demanded.<br /><br />## Step 3<br />The demand curve does not represent the willingness and ability to pay curve. The willingness and ability to pay curve is a different concept that represents the maximum price a consumer is willing to pay for a good or service.<br /><br />## Step 4<br />The demand curve does not represent the marginal cost curve. The marginal cost curve is a different concept that represents the cost of producing one additional unit of a good or service.<br /><br />## Step 5<br />The demand curve does not represent the highest price that someone is willing to pay for an additional unit of a good or service. The highest price a consumer is willing to pay for an additional unit of a good or service is represented by the willingness and ability to pay curve, not the demand curve.