Q3:

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?

1. 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.

2. Severe icing conditions can cause power outages and slow down the work of emergency crews trying to get power restored.

3. 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.

4. 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.

5. 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.

答案A   做的时候就想着要选跟economi有关的,结果5个都排除了,A是不是因为容易坏所以经常要付construction costs呢

答案A   做的时候就想着要选跟economi有关的,结果5个都排除了,A是不是因为容易坏所以经常要付construction costs呢

我想是的，有损坏就有经济损失。

其他的确实是应该用无关排除掉了。

You are right.  However, the most important thing is the

shortening of life.  With the use of salt, the bridge may be

badly damaged in 30 years; with the ECC concrete, may be the

bridge can last for a hundred years.

可是原文并没有说重铺的目的是为了维持或增加桥的寿命，A和

economic grounds根本无关,我实在没法选了E,因为HO说电的价格比除冰盐

便宜得多,那么在说电流用的也比较少,5个选项中唯一能在经济上加强

HO....

希望有NN指点

PS:这一题第一眼A最象答案,但认真看后排除了A,最近做题经常这样,第一

眼看到了正确答案,但仔细推敲后选了一个错误的.....

要支持的是ECC是个好东西虽然成本高，但是deicing其实没那么好虽然便宜

因为：使用deicing做的桥，寿命短，寿命短需要再投入refacing或者reconstruction

E说：电力只在需要的时候才通，但这并没有回击纳税人的看法：ECC制造陈本高

要知道，ECC陈本高，而且还要通电，而deicing 水泥陈本低，还不要通电，这样ECC确实不好，没有回击纳税人的观点。

所以E是错的

A is right

many  thanks !!!!!!