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  3. In an average winter, highway departments spread some ten million tons of salt to keep roads safe. The corrosive effects are wel

In an average winter, highway departments spread some ten million tons of salt to keep roads safe. The corrosive effects are wel

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问题     In an average winter, highway departments spread some ten million tons of salt to keep roads safe. The corrosive effects are well known, but for years they’ve been dismissed with the argument that at around $ 25 a ton, salt is far cheaper than any alternative.
    Lately, economists have added up the actual costs. The Environmental Protection Agency estimates that salt-induced road damage and vehicle corrosion cost $ 3 billion a year. That does not include damage to underground cables, which adds hundreds of millions to utility bills. Nor does it reflect the cost or salty water leaking into roadbeds, which kills evergreens and poisons streams.
    The various costs probably add another $ 2 billion to the national salt bill. Scientists estimate the full economic, or "life cycle", cost for a ton of salt at $ 500, or 20 times the $ 25 purchase price. That begins to make the switch to calcium magnesium acetate (CMA), perhaps the most promising alternative, look practical. CMA costs $ 600 a ton and has minimal side effect. Some researchers believe the cost can be halved by making CMA from waste cheese whey (乳浆).
    While CMA and other alternatives are being researched, many cities and states are cutting back on their use of salt.
In the second sentence of Para. 1, the word "they" refers to______.
选项 A、the corrosive effects
B、the economists
C、the highway departments
D、the roads
答案A
解析 本题是一道测试词汇含义题。问文章第一段第二句话中的代词they指代什么。根据文章上下文，在一个普通的冬天，为保证道路安全，公路部门要撒掉大约1 000万吨食盐。食盐的腐蚀作用是众所周知的，但是，多少年来这些腐蚀作用并未被当成一回事，其理由是：25美元左右一吨食盐，比用任何替代品都便宜。由此我们知道they应该指代的是前文中复数名词。因此，本题的正确答案应是A“盐的那些腐蚀作用”。
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