题目内容
Each year, road accidents kill a million people and injure millions more . The economic costs are greatest for developing countries . Earlier this year , the United Nations called for a campaign to improve road safety .
One way to avoid accidents is better driving . Another is better roads and bridges . Engineers in the Unites States have designed ten new concrete mixtures that they think could make bridges last longer .
Professor Paul Tikalsky leads the experiments by a team at Pennsylvania State University . He says bridges made of concrete now last about twenty-five to thirty-five years . But he says the new mixtures might extend that to seventy –five or even one-hundred years .
Concrete is made of stone , sand , water and cement(水泥). The materials in the cement hold the concrete together . Ancient Romans built with concrete . Yet strengthened concrete bridges did not appear until the late 1800s . People keep looking for new ways to improve concrete . Professor Tikalsky says it is one of the most complex of all chemical systems .
The new mixtures designed by his team contain industrial waste products . He says these make the concrete better able to resist damage from water and salt over time . One of the products is fly ash . This is released into the air as pollution when coal is burned .
Professor Tikalsky says particles (颗粒)of fly ash are almost exactly the same size and chemical structure as Portland cement . This is the most costly material in concrete . So using fly ash to replace some of it would save money .
The federal government is paying for part of the research . Engineers anywhere can use the technology . Professor Tikalsky says some of the ideas have already been put to use in China , the Philippines and other countries .
小题1:Why did the United Nations launch the campaign ?
years .
小题2:What does the underlined word “ this ” in the sixth paragraph refer to ?
小题3:Which of the following statements is TRUE ?
小题4:What does the passage mainly tell us ?
One way to avoid accidents is better driving . Another is better roads and bridges . Engineers in the Unites States have designed ten new concrete mixtures that they think could make bridges last longer .
Professor Paul Tikalsky leads the experiments by a team at Pennsylvania State University . He says bridges made of concrete now last about twenty-five to thirty-five years . But he says the new mixtures might extend that to seventy –five or even one-hundred years .
Concrete is made of stone , sand , water and cement(水泥). The materials in the cement hold the concrete together . Ancient Romans built with concrete . Yet strengthened concrete bridges did not appear until the late 1800s . People keep looking for new ways to improve concrete . Professor Tikalsky says it is one of the most complex of all chemical systems .
The new mixtures designed by his team contain industrial waste products . He says these make the concrete better able to resist damage from water and salt over time . One of the products is fly ash . This is released into the air as pollution when coal is burned .
Professor Tikalsky says particles (颗粒)of fly ash are almost exactly the same size and chemical structure as Portland cement . This is the most costly material in concrete . So using fly ash to replace some of it would save money .
The federal government is paying for part of the research . Engineers anywhere can use the technology . Professor Tikalsky says some of the ideas have already been put to use in China , the Philippines and other countries .
小题1:Why did the United Nations launch the campaign ?
| A．Because the United Nations wanted to reduce road accidents and economic costs |
| B．Because two million people were killed in the accidents . |
| C．Because engineers wanted to design ten new concrete mixtures . |
| D．Because the United Nations made bridges of the new mixtures which could last for about 20 to 35 |
小题2:What does the underlined word “ this ” in the sixth paragraph refer to ?
| A．Fly ash | B．Portland cement | C．Sand | D．Chemical |
| A．Ten new concrete bridges have already been built in the United States . |
| B．A new concrete bridge could last 50 more years than an ordinary concrete one . |
| C．People didn’t know how to build with cement until the late 1800s . |
| D．Water and salt won’t do any damage to bridges over time . |
| A．The causes of road accidents . | B．The advantages of fly ash |
| C．The measures of avoiding road accidents | D．Latest information about long-life concrete bridges |
小题1:A
小题2:B
小题3:B
小题4:D
略
练习册系列答案
相关题目
An electronic voice will distribute stories about the latest events, guided by a program that selects the type of news you want. You’ll even get to choose the kind of voice you want to hear. Want more information on this brief story? A simple touch makes the entire text appear. Save it in your own personal computer if you like. These are among the predictions from communication experts working on the newspapers of the future. Pictured as part of broader home-based media and entertainment systems, computer newspapers will unite print and broadcast reporting, and offer news and analysis with video images of news events. 
and publishers will have to die off before the next generation realizes that the newspaper industry is no longer a newspaper industry. Technology is making the end of traditional newspapers unavoidable.
can be inferred that journali
s