A
A good or service which should be subsidized or provided free in order to encourage its consumption.
B
A good or service which is non diminishable and non exclusive and therefore will not be provided by the free market.
C
A benefit arising from the consumption of a good which is experienced by people other than the immediate consumer of that good.
D
A cost arising from the production of a good which is borne by people other than the immediate producer of that good.
