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A、B、C、D、E为五种气态烃，其中A、B、C都能使酸性KMnO4退色，1molC与2molBr2完全加成，生成物分子中每个碳原子都有一个溴原子，A与C通式相同，A与H2加成可得到B，B与N2密度相同，D是最简单的有机物，E为D的同系物，完全燃烧等摩尔B、E，生成CO2相同，试确定A、B、C、D、E的结构简式．

答案

A、B、C、D、E为五种气态烃，D是最简单的有机物，则D为甲烷，结构简式为CH4；

1molC与2molBr2完全加成，生成物分子中每个碳原子都有一个溴原子，则C含有4个C原子，为1，3-丁二烯与溴发生加成反应，C为CH2=CH-CH=CH2；

A与C通式相同，A与H2加成可得到B，B与N2密度相同，则B的相对分子质量为28，故B为乙烯、A为乙炔，A的结构简式为CH≡CH、B的结构简式为CH2=CH2；

E为D的同系物，属于烷烃，完全燃烧等摩尔B、E，生成CO2相同，则E分子中含有2个C原子，故E为乙烷，结构简式为CH3CH3，

故答案为：A、B、C、D、E的结构简式分别为CH≡CH、CH2=CH2、CH2=CH-CH=CH2、CH4、CH3CH3．

问答题

The American economic system is organized around a basically private-enterprise, market-oriented economy in which consumers largely determine what shall be produced by spending their money in the marketplace for those goods and services that they want most. Private businessmen, striving to make profits, produce these goods and services in competition with other businessmen; and the profit motive, operating under competitive pressures, largely determines how these goods and services are produced. (47)Thus, in the American economic system it is the demand of individual consumers, coupled with the desire of businessmen to maximize profits and the desire of individuals to maximize their incomes that together determine what shall be produced and how resources are used to produce it.
(48)An important factor in a market-oriented economy is the mechanism by which consumer demands can be expressed and responded to by producers. In the American economy, this mechanism is provided by a price system, a process in which prices rise and fall in response to relative demands of consumers and supplies offered by seller-producers. If the product is in short supply relative to the demand, the price will be bid up and some consumers will be eliminated from the market. (49)If, on the other hand, producing more of a commodity results in reducing its cost, this will tend to increase the supply offered by seller-producers, which in turn will lower the price and permit more consumers to buy the product. Thus, price is the regulating mechanism in the American economic system.
The important factor in a private-enterprise economy is that individuals are allowed to own productive resources (private property), and they are permitted to hire labor, gain control over natural resources, and produce goods and services for sale at a profit. (50)In the American economy, the concept of private property embraces not only the ownership of productive resources but also certain rights, including the right to determine the price of a product or to make a free contract with another private individual.
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半剖视图的标注与（）相同。

A.局部剖视图

B.局部剖面图

C.全剖视图

D.剖面图
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