If net exports fall, what actions could a central bank take to stabilize the economy?

Three friends stay in an apartment. Their landlord offers to air-condition the apartment if they pay for the installation charges. Although they all want an air-conditioner, none of them say so. This is an example of the ________

A) free-rider problem B) paradox of thrift C) tragedy of commons D) paradox of plenty

Consider a market in which there is an external cost. A tax can be used to arrive at the efficient market equilibrium because the tax will

A) decrease supply of the good. B) increase supply of the good. C) decrease demand for the good. D) increase demand for the good.