Market Demand via Horizontal Summation

Steps:

• Examine the individual demand curves for Buyer 1 and Buyer 2 from the diagrams.
• For each price level, add the quantities demanded by both buyers to get total market quantity.
• Plot total quantity against price to form the market demand curve.
• Compare the resulting shape to the choice options.

Why C is correct:

• C depicts the horizontal summation of the two downward-sloping individual demands, yielding a steeper overall downward-sloping curve per the law of demand.

Why the others are wrong:

• A shows a vertical summation, which applies to supply, not demand.
• B represents an average of the curves, ignoring total quantity addition.
• D illustrates a single curve without summation, failing to aggregate buyers.

Final answer: C