39.
(A)associated with
(B)thanks to
(C)without
(D)besides

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Public goods are those commodities from whose enjoyment nobody can be effectively excluded. Everybody is free to enjoy the benefits of these commodities, and one person’s utilization does not reduce the possibilities of anybody else’s enjoying the same good. Examples of public goods are not as rare as one might expect. A flood control dam is a public good. Once the dam is built, all persons living in the area will benefit—___36__ their own contribution to the construction cost of the dam. The same __37___ for highway signs or aids to navigation. Once a lighthouse is built, no ship of any nationality can be effectively excluded from the utilization of the lighthouse for navigational purposes. National defense is another example. Even a person who__38___ military expenditures or did not pay any taxes will benefit from the protection provided. It is no easy task to determine the social costs and social benefits ___39__ a public good. There is no practicable way of charging drivers for looking at highway signs, sailors for watching a lighthouse, and citizens for the security provided to them through national defense. Because the market does not provide the necessary signals, economic analysis ___40__ for the impersonal judgment of the marketplace.

It is no easy task to determine the social costs and social benefits (39) associated with a public good.

決定與公共物品相關的社會成本和社會效益並非易事。