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  3. One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile

One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile

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问题     One of the differences between animals and machines is that animal bodies can repair much of the damage that a cruel and hostile world inflicts on them. A machine, by contrast, has to wait for someone to fix it. But that may change if researchers of self-repairing materials have their way. Two groups in America and Britain are trying to create composite materials that mend themselves if they get cracked, in much the same way that an animal’s broken bone heals itself. The difference is that these materials will heal in minutes rather than months.
    Such self-healing composites may take a while to enter everyday use. But if they can be made reliable they will be welcome in high-stress applications. Jeffrey Moore and his colleagues at the University of Illinois are working on the problem by adding extra components to their composites. These composites consist of fibres embedded in a plastic matrix. The main extra component added by Dr. Moore is a sprinkling of tiny capsules containing a chemical. If the composite cracks, the capsules near the crack break open and release the chemical molecules, which link together to form another type of plastic that binds the crack together and heals the material.
    Ian Bond and his colleagues at the University of Bristol’s department of aerospace engineering are taking a slightly different approach. They use glass fibres rather than carbon fibres in their composite and, instead of adding capsules, they have put the healing molecules into the fibres themselves. The molecules in question are the two ingredients of epoxy resin. Half the fibres contain one ingredient and half contain the other. A crack in the material breaks the fibres, releasing the ingredients which react, form more epoxy, and thus mend the crack. The advantage of this approach is that it retains the basic fibre-plus-matrix structure of the material. Adding capsules changes that and risks weakening it. The disadvantage is that capsules are easier to make than hollow, fluid-filled fibres.
    Whichever system is adopted, two further things are needed. One is a way of checking that a component really has healed. The other is a way to top up the healing molecules once some of them have been used. A repaired area would develop a bruise. Topping up the supply of healing fluid might be done by mimicking another biological system—the network of blood capillaries that supplies living tissues with the stuff they need to thrive. Dr. Moore and Dr. Bond are attempting to borrow from nature this way. If they succeed, the machines of the future will have longer and healthier lives.
The passage is mainly about
选项 A、the substitutes for self-healing composites.
B、the differences between animals and machines.
C、different ways of realizing self-recovery.
D、materials capable of repairing themselves under development.
答案D
解析 本文主要是关于[A]自我修复合成材料的替代品。[B]动物和机器之间的不同之处。[C]实现自我修复的不同方法。[D]研制中的自我修复材料。通读全文会发现，文章讲了机器与动物的不同、机器的自我修复材料的不同制造方法以及自我修复的替代材料，但这些只是其中的部分内容。正确答案为“研制中的自我修复材料”。
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