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问题 选择题

含有2～5个碳原子的直链烷烃的沸点和燃烧热的数据见下表：

烷烃名称乙烷丙烷丁烷戊烷
沸点(°C)－88.6－42.1－0.536.1
燃烧热(kJ·mol－1)1560.72219.22877.63535.6
 

根据表中数据，下列判断错误的是(　　)

A．正庚烷在常温、常压下肯定不是气体

B．烷烃的燃烧热和其所含碳原子数基本呈线性关系

C．随碳原子数增加，烷烃的沸点逐渐升高

D．随碳原子数增加，烷烃的沸点和燃烧热都成比例增加

答案

答案：D

由表中给出的数据可知，随着碳原子数的增加，烷烃的沸点逐渐升高，而戊烷的沸点高于常温，所以常温下庚烷是液体，故选项A、C正确；3535.6－2877.6＝2877.6－2219.2＝2219.2－1560.7≈658，所以选项B正确，而沸点的变化没有这种关系，故选项D错误。

单项选择题

The "standard of living" of any country means the average person’s share of the goods and services which the country produces. A country’s standard of living, (1) , depends first and (2) on its capacity to produce wealth." Wealth" in this sense is not money, for we do not live on money (3) on things that money can buy. "Goods" such as food and clothing, and "services" such as transport and " (4) ". A country’s capacity to produce wealth depends upon many factors, most of (5) have an effect on one another. Wealth depends (6) a great extent upon a country’s natural resources. Some regions of the world are well supplied with coal and minerals, and have a fertile soil and a (7) climate; other regions possess none of them.

Next to natural resources (8) the ability to turn them to use. China is perhaps as well (9) as the USA in natural resources, but suffered for many years from civil and (10) wars, and (11) this and other reasons was (12) to develop her resources. (13) and stable political conditions, and (14) from foreign invasion, enable a country to develop its natural resources peacefully and steadily, and to produce more wealth than another country equally well (15) by nature but less well ordered.

A country’s standard of living does not only depend upon the wealth that is produced and consumed (16) its own borders, but also upon what is indirectly produced through international trade. (17) , Britain’s wealth in foodstuffs and other agricultural products would be much less if she had to depend only on (18) grown at home. Trade makes it possible for her surplus manufactured goods to be traded abroad for the agricultural products that would (19) be lacking. A country’s wealth is, therefore, much influenced by its manufacturing capacity, (20) that other countries can be found ready to accept its manufactures.

2（）

A.primary

B.principal

C.foremost

D.uniquely
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单项选择题

如果电子邮件发送后，接收者的计算机没有开机，那么电子邮件将（）。

A．返回到发信人的邮箱里

B．保存在ISP的主机上

C．保存在POP3服务器上

D．保存在SMTP服务器上
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