共用题干 Seeing Red Means Danger AheadThe color red often means danger一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一or________(52)kinds of materials一could one day contain a color-changing material.It will turn red_________(53)a structure collapses or falls apart.The secret__________(54)the color-switching material is。particular typo of molecule(分子).A mole-cule is a group of atoms(原子)held together by chemical bonds. Molecules come_________(55)all shapesand 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)which 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 pro- ject.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 mngi-neers.They need to use the color-changer in big construction projects that will be_________(63)in sun- light. And sunlight will make the rnechanophore'S warning system______(64).Sottos and her fellow scientists still have _________(65)work to do before the color-changing mole-cules can be used outside the lab. _________(51)
A.throw B.prevent C.create D.keep正确答案B
