A tariff is a tax restriction on imported goods.

In the ________________ of externalities, the market equilibrium is ______________ efficient because it maximizes the net social benefit.

a. absence; ecologically b. presence; ecologically c. absence; economically d. presence; economically e. absence; environmentally

Public goods are

a. valuable socially. b. not depletable and not excludable. c. subject to the "free rider" problem. d. All of the above are correct.