In a self-selection problem, the explanatory variables can be:?

In a fixed exchange rate system,

A. The capital account surpluses must offset current account deficits. B. A country can eliminate a surplus of its currency by eliminating its protectionist barriers to trade. C. A balance-of-payments deficit can be corrected by expansionary fiscal and expansionary monetary policies. D. Excess demand for a currency is eliminated by using foreign exchange reserves to increase demand.

In a market for emission permits, firms that emit over their allowed limits

A. must buy more allowances through a trading system. B. are forced to shut down. C. are taxed by the government for the amount of emissions. D. will sell their excess allowances through a trading system.