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题库 / GMATLA-CR-72
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?
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.
Severe icing conditions can cause power outages and slow down the work of emergency crews trying to get power restored.
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.
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.
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.
反驳者是通过cost来说是，那么反驳反驳者就应该也谈成本
d——十分纠结的不相关答案
ECC通过通电的方法来给大桥除冰，并且电力成本比de-icing成本低。但是建造ECC的成本比传统的水泥成本更高，所以从经济角度考虑没有理由用ECC，问support the highway official's proposal in the face of the taxpayer's objection?
CQ方向应为加强ECC+电方案or削弱普通水泥+salt方案
A选项：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. de-icing salt会造成桥的腐蚀，大大缩减桥的使用寿命，其造成的经济损失更严重，correct，指出了salt方案的一个致命的“否定性副作用”！
D选项：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. 仅仅是提出了ECC另外的功能，然而这个功能salt可能也具备同时成本还低，无法反驳taxpayer的观点
只涉及到resurface concrete bridges这一项目的成本问题，有其他的作用和这个项目的成本问题无关
A从成本上反驳，B没有从成本上反驳
ECC通过通电的方法来给大桥除冰，并且电力成本比de-icing成本低。但是建造ECC的成本比传统的水泥成本更高，所以从经济角度考虑没有理由用ECC，问weaken
choice a, de-icing salt会造成桥的腐蚀，大大缩减桥的使用寿命。correct，指出了看似更优方案的一个致命缺陷
choice c, 当到了可能要结冰的天气，冰通常会先在桥的表面形成，随后在和地面接触的车行道上形成。irrelevant，无关结冰的过程
choice e, 如果ECC被用于大桥表面，电流只会在冰即将形成的时候导通。irrelevant，choice e可以解释为什么ECC的电力成本低
反驳要针对对方的观点
D项没有从成本上反驳对方，就是说，即使有其他用途，但是其成本还是高。
A项，不用ECC会减少使用寿命，这样均摊下来，还是可能用ECC会更加便宜，否则很快纳税人还是要掏钱啊！