Market Supply as Sum of Firm Supplies

Steps:

• Define market supply as the total quantity of a good all producers are willing to sell at various prices.
• Recall that market supply curve is derived by horizontally summing individual firms' supply curves.
• Eliminate options unrelated to production aggregation, like consumer income or good types.
• Confirm the core definition matches option C.

Why C is correct:

• Market supply is the horizontal summation of all individual firms' supply curves, as per basic microeconomics, showing total output at each price.

Why the others are wrong:

• A: Market supply can rise from new firms entering or some firms expanding, not requiring all to increase output.
• B: Supply depends on producers' costs and prices, not consumers' income, which affects demand.
• D: Supply curves slope upward for all goods regardless of inferiority, which relates to demand elasticity.

Final answer: C