What represents a demand curve?

The demand curve is best represented by a graph that illustrates the relationship between price and quantity demanded. This graphical representation shows how much of a good or service consumers are willing and able to purchase at different price levels. Typically, the demand curve slopes downward, indicating that as the price decreases, the quantity demanded increases—this reflects the law of demand.

This visual tool is crucial for understanding consumer behavior in response to price changes. It helps economists and businesses analyze how shifts in market conditions, such as changes in consumer preferences or income levels, can affect demand.

The other options do not accurately describe a demand curve. For instance, a diagram showing the quantity supplied addresses the supply side of the market, and a representation of consumer surplus focuses on the benefits consumers receive, which are distinct concepts from demand. A chart displaying production costs over time relates to supply and production analysis, again separate from demand-related factors. Thus, the option that details the relationship between price and quantity demanded is the clear representation of a demand curve.