What is NOT a characteristic of carbon dio

题型:单项选择题

问题:

What is NOT a characteristic of carbon dioxide fire-extinguishing agents?()

A.Effective even if ventilation is not shut down

B.Will not deteriorate in storage

C.Non-corrosive

D.Effective on electrical equipment

考点:航海英语应急部署应急部署题库
题型:单项选择题

对于患者管理的基本内容正确的是()。

A.支持和解释

B.告诫或建议

C.开处方、转诊

D.观察随访、预防

E.以上都对

题型:单项选择题

当业务流量增加,现有交换机不能满足通信需求,就需要扩容,根据预计业务增量,在交换机上插装相关硬件设备,扩充现有容量即可。这些新插装的硬件设备支出相对交换机设备支出而言,可近似的看作()

A、变动成本

B、固定成本

C、边际成本

D、附加成本

题型:单项选择题

Ⅰ、物质的分离和提纯有多种方法。物质分离、提纯方案的设计在科学研究和工业生产中占有十分重要的地位。工业上冶炼铝的原料是铝土矿(主要成分是Al2O3,杂质为Fe2O3、SiO2等,已知SiO2是不溶于水的酸性氧化物,Fe2O3是不溶于水的碱性氧化物)。某研究小组设计的提纯Al2O3的方案如下:

(1)写出沉淀A的化学式:___________________________________________________。

(2)加入过量的NaOH溶液,过滤后的滤液中含有的溶质有________________________。

(3)写出由沉淀A—→Al2O3的化学方程式:________________________,通入过量CO2生成沉淀A时反应的离子方程式为_______________________________________________。

Ⅱ、按照要求回答下列问题:

A、B、C、D、E是常见化合物或单质,有如下转化关系 (略去条件和副产品)。

(1)若A为黄绿色气体单质,D、E为生活中常见的两种金属,其中E是一种红色光亮的物质。

① 写出向B的溶液中加入足量D的离子反应方程式_____________________________________。

②向①所得的溶液中加入NaOH溶液,并在空气中放置的现象是:_________________________,写出固体在空气中放置的化学反应方程式:__________________________________________。

题型:单项选择题

NASA has opened the door to the next generation of space discovery by announcing great plans for a base for humans to live on the surface of the moon forever.

The project to build a base on the moon will begin soon after 2020, with astronauts living there within four years.

The project comes after several excellent scientists and environmentalists asked humans to look beyond Earth to ensure the survival of the species (物种).

Eventually, the moon will be a base for humans to explore the solar system and one day land on Mars.

NASA began planning for the first moon landing since 1972 when George Bush, the US president, announced his new plan for space exploration four years ago.

NASA has already talked about the design of the Orion spacecraft that will replace the old space shuttle fleet in 2010.

The plan for the moon base, however, is the first detailed explanation of how NASA intends to prepare for the first manned exploration of deep space and a possible Mars mission within 30 years.

Scientists also believe that the south pole on the moon contain rich natural gases such as the rare helium-3 that could be used as fuel for the generation of nuclear power. Besides, teams of astronauts living there for six months at a time would mine for hydrogen and oxygen to make water and possibly rocket fuel.

小题1:When was the plan to explore space first announced according to the passage?

A.In 1972.

B.In 1950.

C.In 1968.

D.In 2020.小题2:The reasons why NASA has begun the plan to explore space include the followings except ________.

A.to protect Earth

B.to explore deep space

C.to finish Mars mission

D.to show how powerful the USA is小题3:In the future, when people fly to the moon, they will probably not bring with them too much ________

A.hydrogen

B.food

C.oxygen

D.water小题4:The passage mainly talks about ________.

A.the USA’s new plan for space exploration

B.how to build a base on the moon

C.why to ensure the survival of the species

D.where to get new natural resources

题型:单项选择题

配气相位的四个角度中,()的大小对发动机充气性能影响最大。

A.进气提前角

B.进气迟后角

C.排气提前角

D.排气迟后角

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