阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。

　　A huge cloud of dust rose and an overpass disappeared．This was the scene in Zhuzhou, Hunan Province on May 17．Nine people were killed and 16 injured．

　　Things were similar last year in the Sichuan earthquake．Thousands of people were buried in the ruins and lost their lives．What if we could have warned them?

　　People are always trying their best to find a way of preventing buildings’ collapse．Better materials and technology help, but they are not a solution．

　　Just like humans, a building has its own life cycle from “birth” to “death”．If we know when a building is going to collapse, we can repair it in advance or get out of it before it falls．

　　Now, scientists at the University of Illinois have developed a material that turns red before it breaks．The invention could be used in things like climbing ropes or bridge supports．

　　The research was led by Nancy Sottos, a professor at the university's Beckman Institute, and Douglas Davis, a graduate research assistant．

　　The secret behind the color-changing material is a type of molecule(分子)．A molecule is a group of atoms held together by chemical bonds．Imagine you and your friends standing in a circle, holding hands．Each person stands for one atom, your hands represent the bonds, and the entire circle represents a molecule．If one person lets go of his or her hands, the molecule changes color．

　　The research team put the molecule into a soft material．When the researchers stretched(拉伸)the material, it turned bright red for a few seconds before it broke into two pieces．When they repeatedly stretched and relaxed the material, without breaking it, it only turned a little red．

　　The major problem is that light can get rid of the red color．When the team shone bright light on the molecule, the broken bond was fixed, and the color disappeared．

　　If the bright light keeps the red color from appearing, the material's warning system will be useless．Scientists still have a lot of work to do before the color-changing molecules can be used outside the lab．

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阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项。

　　Scientific experts from around the world are genuinely predicting that 3 years from now, all life on Earth could well finish．Some are saying it'll be humans that set it off．Others believe that a natural phenomenon will be the cause．And the religious folks are saying it'll be God himself who presses the stop button．．．Seven reasons are going about why the world will end in 2012 and netizens have started a discussion in the forum．

　　1．Mayan Calendar

　　The first mob to predict 2012 as the end of the world were the Mayans, a bloodthirsty race that were good at two things：Building highly accurate astrological(占星术的)equipment out of stone and sacrificing virgins．

　　Thousands of years ago they managed to calculate the length of the lunar moon as 329.53020 days, only 34 seconds out．The Mayan calendar predicts that the Earth will end on December 21, 2012．Given that they were pretty close to the mark with the lunar cycle, it's likely they’ve got the end of the world right as well．

　　2．Sun Storms

　　Solar experts from around the world monitoring the sun have made an extremely discovery：our sun is a bit of conflict．The energy output of the sun is, like most things in nature, cyclic(循环的), and it's supposed to be in the middle of a period of relative stability．However, recent solar storms have been bombarding the Earth with so much radiation energy, and it's been knocking out power grids and destroying satellites．This activity is predicted to get worse, and calculations suggest it will reach its deadly peak sometime in 2012．

　　3．The Atom Smasher

　　Scientists in Europe have been building the world's largest particle accelerator(粒子加速器)．Basically it's a 27km tunnel designed to break atoms together to find out what makes the Universe tick．However, the device has caused serious concern, with some scientists suggesting that it's properly even a bad idea to turn it on in the first place．They’re predicting all manner of deadly results, including mini black holes．So when this machine is fired up for its first serious experiment in 2012, the world could be squeezed into a super-dense drop the size of a basketball．

　　4．The Bible says…

　　If having scientists warning us about the end of the world isn't bad enough, religious folks are getting in on the act as well．Interpretations of the Christian Bible reveal that the date for Armageddon, the final battle between Good and Evil, has been set down for 2012．The I Ching, also known as the Chinese book of Changes, says the same thing, as do various sections of the Hindu teachings．

　　5．Super Volcano

　　Yellowstone National Park in the United States is famous for its thermal springs and Old Faithful geyser．The reason for this is simple-it's sitting on top of the world's biggest volcano, and geological experts are beginning to get nervous sweats．The Yellowstone volcano has a pattern of erupting every 650, 000 years or so, and we’re many years overdue for an explosion that will fill the atmosphere with ash, blocking the sun and suddenly moving the Earth into a frozen winter that could last up to 15, 000 years．The pressure under the Yellowstone is building steadily, and geologists have set 2012 as a likely date for the big bang．

　　6．The Physicists

　　This one is case of bog-simple maths mathematics．Physicists at Berkley University have been dealing with the numbers and they have determined that the Earth is well overdue for a major catastrophic event．Even worse, they’re claiming their calculations proof that we’re all going to die, very soon-while also saying their prediction comes with a certainty of 99 percent-and 2012 just happens to be the best guess as to when it occurs．

　　7．Slip-Slop-Slap-BANG!

　　We all know the Earth is surrounded by a magnetic(磁的)field that shields us from most of the sun's radiation．What you might not know is that the magnetic poles we call north and south have a bad habit of swapping places every 750, 000 years or so-and right now we’re about 30, 000 years overdue．Scientists have noted that the poles are drifting apart roughly 20-30kms each year, much faster than ever before, which points to a pole-shift being right around the corner．While the pole shift is underway, the magnetic field is disrupted and will eventually disappear, sometimes for ups to 100 years．The result is enough UV(紫外线的)outdoors to crisp your skin in seconds, killing everything it touches．

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