Seeing Red Means Danger Ahead The color red often means danger-and by paying attention,accidents can be prevented.In the futu

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问题                        Seeing Red Means Danger Ahead
   The color red often means danger-and by paying attention,accidents can be prevented.In the future,the color red also may help【51】______danger at construction sites.Thanks to new work by engineers,bridge supports-or【52】______kinds of materials-could one day contain a color-changing material.It will turn red【53】______a structure collapses or falls apart.
   The secret【54】______the color-changing material is a particular type of molecule(分子).A molecule is a group of atoms(原子)held together by chemical bonds.Molecules come【55】______all shapes and sizes,and make up【56】______you can see,touch or feel.How a molecule behaves depends on【57】______kinds of atoms it contains,and how they’re held together.
   When a polymer(聚合物)containing a color-changing molecule called a mechanophore(机械响应性聚合物)is about to break,it produces a【58】______.When a polymer with mechanophore molecules becomes“injured”or【59】______,one of the mechanophore bonds【60】______and the material turns red.“It’s a really simple detection method,”says Nancy Sottos,one of the scientists who worked on the project.Sottos and her team tested the color-changing polymers in their lab.The test【61】______ proved encouraging.
   There is a way to get rid of the red color:light.When a bright light is shone on the mechanophore, the broken bond is fixed-and the red color【62】______.This“self-healing”may be a problem for engineers.They need to use the color-changer in big construction projects that will be【63】______,in sunlight.And sunlight will make the mechanophore’s warning system【64】______.
   Sottos and her fellow scientists still have【65】______work to do before the color-changing molecules can be used outside the lab.

选项 A、on
B、behind
C、under
D、down

答案B

解析 此处考查“……背后的秘密”,behind表示“后面的”,故选B。
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