问题 选择题

下列物质的用途中利用了氧化还原反应原理的是( )

A.用明矾净水

B.用“84消毒液(有效成分为NaClO)”消毒

C.用食盐腌渍食物

D.用小苏打治疗胃酸过多

答案

答案:B

A是利用明矾水解生成的氢氧化铝吸附造成的。B是利用次氯酸钠的氧化性造成的。C是利用盐溶解使食物和食物所处的环境中的钠离子和氯离子浓度升高,几乎没有生物能在这种环境下生存,食物不易变质。D是利用小苏打的碱性,答案选B。

单项选择题
阅读理解

阅读理解。

     A baby born in India has been declared the world's seven billionth person by child rights group

Plan International. Baby Nargis was born at 07:25 local time(01:55GMT)in Mall village in India's

Uttar Pradesh state. Plan International says Nargis has been chosen symbolically as it is not possible

to know where exactly the seven billionth baby is born. In addition to baby Nargis in India,Bangladesh,

the Philippines and Cambodia have all identified seven billionth babies. The United Nations estimated

that on Monday 31 October. the world's population would reach seven billion.

     Populations are growing faster than economies in many poor countries in Africa and some in Asia.

At the same time,low birth rates in Japan and many European nations have raised concerns about labor

shortages.

     Population experts at the United Nations estimated that the world reached six billion in October

1999. They predict nine billion by 2050 and ten billion by the end of the century.  China's population

of one and a third billion is currently the world's largest. India is second at 1. 2 billion. But India is

expected to pass China and reach one and a half billion people around 2025.

     India will also have one of the world's youngest populations. Economists say this is a chance for a

so-called. demographic dividend. India could gain from the skills of young people in a growing economy

at a time when other countries have aging populations. But economists say current rates of growth,

although high,may not create enough jobs. Also,the public education system is failing to meet demand

and schooling is often of poor quality. Another concern is health care. Nearly half of India's children

under the age of five are malnourished(营养不良).

     Michal Rutkowski,the director of human development in South Asia at the World Bank, says reaching

seven billion people in the world is a good time for a call to action. He says,"I think the bottom line of

the story is that the public policy needs to become really,really serious about sex equality and about

access to services-to fight against malnutrition,and to provide for access to health services,water and

schooling. "

1. What is true about the world's seven billionth person?

A. Baby Nargis is not the only child chosen as the seven billionth baby.

B. Baby Nargis has been chosen carefully so it is exactly the seven billionth baby.

C. Three countries have all declared Baby Nargis as the seven billi011th baby.

D. The United Nations declared Baby Nargis as the world's seven billionth person.

2. Which of the following problems do many European countries worry about?

A. Labor shortage.    

B. Poor health care.

C. Not enough jobs.

D. Schooling of poor quality.

3. According to population experts,how long will it take for population to grow from six billion to nine

billion?

A. About 12 years.  

B. About 40 years.  

C. About 50 years.  

D. About 110 years.

4. What does the underlined phrase"demographic dividend"in the fourth paragraph refer to?

A. Possibility of lower birth rate.

B. Benefit gained by working young people.

C. Chances for more employment.

D. Disadvantages caused by aging population.

5. Which of the following public policies does Michal Rutkowski call on?

A. To encourage late marriage.    

B. To reduce world's population.

C. To gain economic equality.  

D. To improve health and education.