Horizontal Summation of Individual Demands

Steps:

• Identify individual demand curves showing quantity demanded by each consumer at various prices.
• For each price level, sum the quantities demanded across all consumers.
• Plot these total quantities against prices to form the market demand curve.
• This horizontal addition reflects aggregate consumer behavior for private goods.

Why B is correct:

• Market demand is defined as the horizontal summation of individual demand curves, aggregating quantities at each price per the law of demand.

Why the others are wrong:

• A: Consumer surplus measures welfare, not demand quantities.
• C: Elasticity describes responsiveness, not the curve itself.
• D: Multiplying price by quantity gives revenue, not the demand relationship.

Final answer: B