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Highway Official: When resurfacing our concrete bridges, we should use electrically conductive concrete (ECC) rather than standard concrete. In the winter, ECC can be heated by passing an electric current through it, thereby preventing ice buildup. The cost of the electricity needed is substantially lower than the cost of the de-icing salt we currently use.
Taxpayer: But construction costs for ECC are much higher than for standard concrete, so your proposal is probably not justifiable on economic grounds.
Which of the following, if true, could best be used to support the highway official’s proposal in the face of the taxpayer’s objection?
A. The use of de-icing salt causes corrosion of the reinforcing steel in concrete bridge decks and damage to the concrete itself, thereby considerably shortening the useful life of concrete bridges. B. Severe icing conditions can cause power outages and slow down the work of emergency crews trying to get power restored. C. In weather conditions conducive to icing, ice generally forms on the concrete surfaces of bridges well before it forms on parts of the roadway that go over solid ground.ice D. Aside from its potential use for de-icing bridges, ECC might also be an effective means of keeping other concrete structures such as parking garages and airport runways ice free. E. If ECC were to be used for a bridge surface, the electric current would be turned on only at times at which ice was likely to form. B不也说了危害了吗？为什么他不对？ When storing Renaissance oil paintings, museums conform to standards that call for careful control of the surrounding temperature and humidity, with variations confined within narrow margins. Maintaining this environment is very costly, and recent research shows that even old oil paint is unaffected by wide fluctuations in temperature and humidity. Therefore, museums could relax their standards and save money without endangering their Renaissance oil paintings.
Which of the following is an assumption on which the argument depends?
A. Renaissance paintings were created in conditions involving far greater fluctuations in temperature and humidity than those permitted by current standards. B. Under the current standards that museums use when storing Renaissance oil paintings, those paintings do not deteriorate at all.
C. Museum collections typically do not contain items that are more likely to be vulnerable to fluctuations in temperature and humidity than Renaissance oil paintings D. None of the materials in Renaissance oil paintings other than the paint are vulnerable enough to relatively wide fluctuations in temperature and humidity to cause damage to the paintings. Most Renaissance oil paintings are stored in museums located in regions near the regions where the paintings were created. A为什么不能选？谢谢 | 
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发表于 2009-8-9 07:16:00
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