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  3. The first bicycles were made of wood. Cycle manufacturers then switched to steel tubes. These days, for high-end bikes where wei

The first bicycles were made of wood. Cycle manufacturers then switched to steel tubes. These days, for high-end bikes where wei

admin2013-10-22  124
问题     The first bicycles were made of wood. Cycle manufacturers then switched to steel tubes. These days, for high-end bikes where weight is at a premium, they use aluminium alloys(铝合金)or even carbon fibre. But Izhar Gafni, an amateur cyclist who owns a number of such fancy bikes, wonders whether the original inventors had a point. He proposes to go back to using wood—or, rather, a derivative(衍生物)of wood, namely cardboard.
    Mr. Gafni, who is based in Ahituv, Israel, spent years trying to work out how to make a cardboard bicycle able to support the weight of a human being. The trick is twofold. First, he folds the cardboard commercial-grade material, made from recycled paper to increase its strength. Then, once it is folded, he treats the result with a proprietary resin(树脂)that holds it in shape and stiffens it, before cutting it into the form of the component required. A second application of resin renders the component waterproof, and a lick of lacquer(漆)makes it look good. The result, Mr. Gafni claims, is stronger than carbon fibre.
    The bike’s frame, wheels, handlebars and saddle are all made of cardboard in this way, and then fitted together. The tyres—again harking back to the early days of cycling—are composed of solid rubber, which is recycled from old car tyres. That makes the ride a little harder than if the tyres were pneumatic(充气轮胎的), but means they cannot be punctured.
    The chain is also made from car-tyre rubber. The pedals are plastic recycled from bottles and the brakes are recycled too, though Mr. Gafni is not yet ready to disclose the details. The finished product weighs 9kg, a bit less than an ordinary bike, and can carry a rider weighing 220kg.
    Mr. Gafni’s target market is the poorer countries of the world. Because manufacturing the cardboard bike will, he reckons, cost $9-12 a unit, his design is far more affordable than a steel-framed bike. But people in rich countries may be interested too. In Tel Aviv, the commercial capital of Mr. Gafni’s native land, 2 000 stolen bikes were recently put on display by police, for their owners to claim. If bicycles cost less than the locks that chained them to lampposts, thieves might not think it worthwhile to steal them.
What is the major reason for having solid rubber tyres for the cardboard bicycle?
选项 A、They help lower the cost.
B、They are environment friendly.
C、They ensure the safety of the rider.
D、They are more endurable.
答案D
解析 推理判断题。由定位句可知，用实心橡胶做成的轮胎使得它不容易被刺破，因此D)“它们更耐用”符合题意。
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