Short-run market supply aggregation assumes ceteris paribus conditions

Steps:

• Individual firm supply curves show quantity supplied at different product prices, holding other factors constant.
• Aggregate by summing quantities from all firms at each price level to form the market supply curve.
• In the short run, number of firms, input prices, and technology remain fixed.
• Product price varies to trace the entire market supply curve.

Why B is correct:

• The market supply curve is defined as the relation between quantity supplied and product price, so price changes along the curve (per the law of supply).

Why the others are wrong:

• A: Number of firms is fixed in the short run, treated as constant during aggregation.
• C: Factor prices are assumed constant in the short run, not varying with output.
• D: Technology is fixed in the short run, unaffected by aggregation.

Final answer: B