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 (顆粒)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 .
小題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
years .
小題2:What does the underlined word “ this ” in the sixth paragraph refer to ?
A．Fly ashB．Portland cementC．SandD．Chemical
小題3:Which of the following statements is TRUE ?
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 .
小題4:What does the passage mainly tell us ?
A．The causes of road accidents .B．The advantages of fly ash
C．The measures of avoiding road accidentsD．Latest information about long-life concrete bridges

小題1:A
小題2:B
小題3:B
小題4:D
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An Experiment
Materials: Newspaper, ‘ACE’ hardware ruler (1/8 “think”), a flat table.
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Procedure:

First put a thin ruler on a flat table with a little
less than half of it hanging off the edge of the table
(see the drawing below). Next place a sheet of newspaper
over the ruler flat against the table. Make sure to have
as little air as possible under the paper so that the fold line of the newspaper is at the ruler. Then quickly strike the end of the ruler hanging off the edge of the table. If you strike it quick enough, the ruler will break near the table edge.
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The research has caused a great deal of argument. Some think it is a bad idea, While others support it.
Supporters say it could lead to pills that prevent or treat soldiers' troubling memories after war. They say that there are many people who suffer from terrible memories.
"Some memories can ruin people's lives . They come back to you when you don't want to have them in a daydream or nightmare. They usually come with very painful emotions," said Roger Pitman, a professor of psychiatry at Harvard Medical School. "This could relieve a lot of that suffering."
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"All of us can think of bad events in our lives that were horrible at the time but make us who we are. I'm not sure we want to wipe those memories out, "said Rebecca Dresser, a medical ethicist.
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C. a way of erasing painful memories  D. an argument about the research on the pill
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C. prevent body producing certain chemicals
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