[单项选择]Tariffs may ______ on commodities leaving an area or on merchandise entering an are
A. A． levyB. be leviedC. effectD. be effected

[单项选择]Tariffs may （） on commodities leaving an area or on merchandise entering an area.
A. levy
B. be levied
C. effect
D. be effected

[单项选择]People in a large area may possess the same DNA thread because


A. DNA is characteristic of a region.
B. they are beyond doubt of common ancestry.
C. DNA strand has the ability to identify individuals.
D. their unique identification can be provided via DN

[单项选择]The price of the real estate in this area may ________ to unexpected values, so everyone should be conscious of the maximum price that he would want to pay for a particular property.


A. stagger
B. shrink
C. soar
D. suspend

[单项选择]What may be the reason for human being's leaving the stage


A. D．The command of DN

[单项选择]Massive database management may be one area that could be ______ by optical technology.


A. presided
B. occupied
C. operated
D. dominated

[单项选择]GATT means ( ) Agreement on Tariffs and Trade
A. Good
B. General
C. Gross
D. Guarantee

[单项选择]GATY means （） Agreement on Tariffs and Trade
A. Good
B. General
C. Gross
D. Guarantee

[单项选择]GATF means ( ) Agreement on Tariffs and Trade.
A. Good
B. General
C. Gross
D. Guarantee

[单项选择]

Passage One
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--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 benef
A. because the Americans want to appear rich
B. because they are smaller, cheaper and easier to use
C. because they can help Americans do everything
D. because 'they can type letters