气焊紫铜要求使用______。A.中性焰 B.碳化焰 C.氧化焰 D.弱碳化焰

题型:单项选择题

问题:

气焊紫铜要求使用______。

A.中性焰

B.碳化焰

C.氧化焰

D.弱碳化焰

考点:焊工高级焊工焊工高级
题型:单项选择题

阅读理解。

    Every year thousands of people get hurt or die when they are crossing the road. Most of these people

are old people and children. Old people often get hurt or die because they can't see or hear very well.

Children usually meet with accidents because of their carelessness. They forgot to look and listen before

they cross the road.

    How can we lessen (减少) traffic accidents? All of us must obey the traffic rules. For the drivers,

they shouldn't drive too fast. If they drive too fast, it will be very difficult to stop the cars in a very short

time. For the pedestrians (行人), it's very important to be careful when they are walking on the road.

Therefore, when we walk across the road, we must try to walk along the pavements. We must stop and

look both ways before crossing the road. Look left first, next look right, then look left again. Only when

we are sure that the road is clear, we can cross it. The right way to cross the road is to walk quickly. It's

not safe to run. If people run across the road, they may fall down. Teens should try to help children, old

people or blind people to cross the road, and never play in the street.

1. Which of the following is NOT the right way to cross the road? [ ]

A. Stop and look both ways.

B. Run quickly.

C. Make sure that the road is clear.

D. Walk quickly.

2. Why do most old people often get hurt or die when they are crossing the road? [ ]

A. Because they can't see or hear very well.

B. Because they forget to look and listen.

C. Because they are not careful.

D. Because they often run across the road.

3. The best title for this article may be           . [ ]

A. How to lessen traffic accidents?

B. How to cross the road?

C. Please obey the traffic rules.

D. Meeting with traffic accidents.

4. As a student, you can            to try to lessen traffic accidents. [ ]

A. let drivers drive slowly

B. play in the street carefully

C. help children to cross the road

D. run across the road quickly

题型:单项选择题

某研究性学习小组用食盐、二氧化锰和浓硫酸共热反应制备氯气,并进行氯气性质实验.其中部分实验装置如图所示:

请填写下列空白:

(1)上图中,氯气制备装置正确的是______,尾气处理装置正确的是______.(填标号字母)

(2)在取用浓硫酸时,如果不慎将少量浓硫酸溅在手上,应立即采取的处置方法是:______.

(3)某同学做了两个实验:①将氯气通入到含有淀粉的碘水溶液中,蓝色消失(生成了碘酸).②停止通入氯气后向溶液中加入一定量的过氧化氢,又出现蓝色,并有气泡产生.请用化学方程式表示上述变化:

①______;

②______.

(4)实验完毕,可选用______(填标号字母)清洗附着在烧瓶内壁上的固体残留物.

A、氯化钠溶液        B、酸化的硫酸亚铁溶液    C、浓盐酸    D、酒精溶液.

题型:单项选择题

儒学教育官方化和制度化的标志是

A.孔子开创私人讲学之风

B.汉武帝创设太学

C.隋朝科举制度的创立

D.汉朝八股取士

题型:单项选择题

分布式数据库系统的分片透明性位于______。

A.全局模式与全局概念模式之间

B.分片模式与分配模式之间

C.全局概念模式与分片模式之间

D.分配模式与局部概念模式之间

题型:单项选择题

扬声器系统工作的最基本条件是:所连接的两只扬声器()一致。

A、相位

B、体积

C、形状

D、功率

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