中等ECON-MINT-011
A factory dumps untreated wastewater as it produces more. This negative production externality means:
A. Marginal social cost is above marginal private cost, and the market quantity is too high✓ 答案
B. Marginal social benefit is below marginal private benefit, and output is too low
C. The demand curve must be perfectly inelastic
D. The output is a public good
解說
The external cost is on the production side, so MSC lies above MPC and the uncorrected quantity is above the social optimum. Option B describes a different gap. Rival, excludable parts are not a public good.