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?goods.Once the dam is built,all persons living in the area will benefit--irrespective of their own?contribution to the construction cost of the dam.The same holds tree 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 voted?against military expenditures or did not pay any taxes will benefit from the protection afforded.
It is no easy task to determine the social costs and social benefits associated with public goods.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 has to be substituted for the impersonal?judgement of the marketplace.
Which of the following would NOT be an example of public goods as described in the passage?
【考情点拨】推理判断题。【应试指导】从文章第一、二段可知，公共商品是每个人都可免费享用的商品，如水坝，公路标志等。由此推知，四个选项中，桥梁、消防车、交通灯都是公共商品，只有A项不是公共商品。
