问题 选择题

NH3、H2S等是极性键构成的极性分子,CO2、BF3、CCl4等是极性键构成的非极性分子。根据上述事实,通过比较归纳可推出ABn型分子是非极性分子的经验规律是[ ]

A.分子中不含有H原子的分子是非极性分子

B.在ABn分子中A原子的所有价电子都参与成键的是非极性分子

C.ABn分子中每个共价键的键长都相等的分子是非极性分子

D.在ABn分子中A的相对原子质量小于B的相对原子质量时为非极性分子

答案

答案:B

完形填空

阅读下面短文,并按照题目要求用英语回答问题(请注意问题后词数要求)。

Poverty today is a major global issue. Although there are all kinds of definitions used to explain it, in simple words, it means the inability of a person to even get his basic needs of food, shelter, clothing, safe drinking water, health and education. Poverty can be found in each and every corner of the world, although the causes may differ from country to country. Given below are the main causes of poverty in the world today.

Overpopulation is one of the main causes behind the threatening of poverty on an individual level as well as a social level. This is simple math: If there are more mouths to feed and less income, definitely much will remain poor.

Another theory which is used as an explanation for poverty is lack of education. If you look at any of the underdeveloped countries, you will find that the level of education there is very low. Lack of education means lack of employment opportunities, thus leading to unemployment coupled with poverty in the future.

Moving away from one’s own homeland to another city or country in search of employment leads to poverty too. It may take these people a lot of time to find jobs. Meanwhile, they live in bad conditions. The cost of living in the city or country is most of the time too high for them.

There may be other causes of poverty like the change in business. For example, in America, a couple of decades ago, heavy industry flourished ,which employed a lot of African-American people. But now, the focus is more on information technology and health care, both of which employ only skilled and trained people. This has led to unemployment among African-Americans.

Poverty has many ill effects on society. That’s why steps should be taken to get rid of it!

小题1:What’s the meaning of the underlined word “flourished” in Paragraph 5?(No more than 5words)

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小题2:Why is overpopulation a cause of poverty today?(No more than 12 words)

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小题3:What’s the situation of education in underdeveloped countries?(No more than 8 words)

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小题4:What does the passage mainly talk about?(No more than 10 words)

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小题5:In your opinion, what’s the most significant cause of poverty today? Please give your reason.(Open)

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单项选择题

阅读下面短文,回答下 * * 道题。

几个月前,来自一些地方的研究人员演示了使光以每秒17米的缓慢速度通过一堆冰冷的钠原子的过程。但是把原子冷却到接近绝对零度是非常困难的,要使以慢光为基础的应用能够变为现实,需要采用简单一些的方法。

德克萨斯州农业机械大学的韦尔奇博士意识到,在冰冷的钠原子中使光速降低的基本原理在热的铷原子中也同样适用。用热的铷原子做实验要简单得多,它包括把一个装有固体铷金属的特殊的透明容器(称为“小室”)加热到大约100℃,然后把两束经过细微调节、波长略微不同的激光射入“小室”。

即使穿过普通的透明的材料,比如玻璃或水,光速也会略微降低,因为光会与组成材料的原子相互作用。但是在这种情况下,影响是微弱的,并且任何加强有力种影响的试图都会导致激光的吸收。因此,重要的是使光的速度降低,而且不至于被吸收。韦尔奇博士通过“小室”做到了这一点。这种方法把铷原子置于一种非常微妙的量子状态中,在这种状态下铷原子不能吸收光。同时,两束光的相互作用产生了另外一束波长很长的光,这束光的传播速度

比原先两束光的速度要慢得多。

降低光速能获得诸如非线性等其他一些效应。在大多数情况下,光的行为是线性的;把入射到玻璃上的光的强度增加一倍,穿过玻璃的光的强度也会增加一倍。但是,非线性意味着入射光的微小变化会导致透射光的巨大改变。正是这种性质使光学开关的设计者们兴奋不已。

加利福尼亚大学的工程师阿塔奇认为,人们在通过光缆传送光脉冲时,常常需要把某个用来与其他信号作对比的信号延迟一段时间。目前的做法是把其中一个脉冲沿着为此目的而专门建造的很多光纤发送出去,而采用一个大小为1升、装满高温铷气的“小室”能够达到同样的目的并且更加有效。

韦尔奇小组的成员卡什说,装满铷气的“小室”在改变激光束以产生难以获得的波长方面极其有效。他们已在考虑运用这个原理制造一个廉价、高效的紫外线源,由于紫外线波长短,因此可以用宋读取刻录的光盘等媒介上的形状更小、排列更紧密的数据。

根据本文提供的信息,以下推断正确的一项是()。

A.利用钠原子降低光速的代价要小于利用铷气

B.光通过高温铷气时,其传播的速度也会降低.

C.紫外线的波长短,所以传播的速度比较慢

D.目前以慢光为基础的应用已经成为现实