搜题请搜索小程序“爱下问搜题”
问题 多选题

下列金属能在空气中表面形成一层致密氧化物薄膜的是（　　）

A．铁

B．铜

C．铝

D．镁

答案

根据金属的性质，活泼金属镁和铝在空气中易与氧气反应，在表面生成一层致密的氧化膜氧化镁（氧化铝），该氧化膜可以保护内层金属不被继续氧化．

故选CD．

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
查看答案
单项选择题

下表是某施工项目的数据资料，有关该数据资料的描述，错误的是（）。

A.第四个月的计划支出是45万元

B.若表中所列各工程的施工速度相同且均按计划顺利进行，则屋面工程与室内设施安装可以同时完工

C.基础施工与主体工程施工在进度上有一个月的搭接

D.若表中所列各工程的施工速度相同且均按计划顺利进行，截止到8月底，砌筑工程还有三分之一的工程量未完成
查看答案