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Similar things continuously happened in Haiti and Chile. Thousands of people were buried in the
earthquake and lost their lives. What if we could have warned them? People are always trying hard
to find a way of preventing building collapsing (倒塌). Better materials and technology help, but are
not a solution. Just like humans, a building has its own life circle from "birth" to "death". If we know
when a building is going to collapse, we can repair it in advance or get out 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 secret behind the
colorchanging material is a type of molecule (分子).  A molecule is a group of atoms held together by
chemical bonds (化学键).  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 (拉紧) the material, it turned bright red
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, light can get rid of the red color. When the team shone a bright light on the
molecule, the broken bond was fixed, and the color disappeared. If 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  colorchanging  molecule  can  be  used  outside the lab.
1. The passage mainly about ________.
A. a way of preventing buildings from breaking down
B. a way of warning before buildings collapse
C. a series of earthquakes in Haiti and Chile
D. a newlydiscovered structure of a molecule
2. According to the passage, we can conclude that ________.
A. scientists have found the life circle of buildings from "birth" to "death"
B. there are problems to solve before putting the new material to use
C. bright light makes the red color visible to human eyes
D. the new material is unlikely to be used in building bridges
3. The colorchanging molecule can ________.
A. remind people to leave buildings before they fall
B. help building materials get stretched if necessary
C. prevent the earthquake from killing people
D. make building materials much stronger
4. The warning system is based on the fact that ________.
A. red color won't show up when it meets bright light
B. a building has its own life circle of "birth" to "death"
C. a material with a certain type of molecule can turn red when stretched
D. the broken bond will fix itself when a molecule meets bright light

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