Public goods are those commodities whose enjoyment nobody can be effectively excluded.Ev

erybody 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------irrespective of their own contribution to the construction cost of the dam.The same holds true 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 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 has to be substituted for the impersonal judgement of the marketplace.

1.With what topic is the passage mainly concerned？

A.Mechanisms for safer navigation.

B.The economic structure of the marketplace.

C.A specific group of commodities.

D.The advantage of lowering taxes.

2.Which of the following marks the feature of public goods？

A.Each citizen has a share of the ownership of the commodity.

B.No one is excluded from the benefits of the goods.

C.People can enjoy the utilization of them if they contribute to it.

D.The use of them is determined by how much one pay.

3.According to the passage, finding out the social costs of a public good is a （）.

A.difficult procedure

B.daily administrative duty

C.matter of personal judgement

D.citizen's responsibility

4.To find out the market for public goods, people need to （）.

A.watch out for the necessary market signals

B.invent a practicable way of charging users

C.make impersonal judgement of the marketplace

D.do economic analysis of their costs and benefits

5.Which of the following statements best describes the organization of the first two paragraphs？

A.Suggestions for the application of an economic concept are offered.

B.Several generalizations are presented from which various conclusions are drawn.

C.Persuasive language is used to argue against a popular idea.

D.A general concept is defined and then examples are given.