That the application of new technology can increase the productivity of existing coal mines is demonstrated by the case of Tribnia’s coal industry.  Coal output per miner in Tribnia is double what it was five years ago, even though no new mines have opened.

Which of the following can be properly concluded from the statement about coal output per miner in the passage?

1. If the number of miners working in Tribnian coal mines has remained constant in the past five years, Tribnia’s total coal production has doubled in that period of time.

2. Any individual Tribnian coal mine that achieved an increase in overall output in the past five years has also experienced an increase in output per miner.

3. If any new coal mines had opened in Tribnia in the past five years, then the increase in output per miner would have been even greater than it actually was.

4. If any individual Tribnian coal mine has not increased its output per miner in the past five years, then that mine’s overall output has declined or remained constant.

5. In Tribnia the cost of producing a given quantity of coal has declined over the past five years.

题中给出的信息是：在没有开新矿的前提下，该地区每家煤厂的产量比五年前翻了一番。

求：根据该信息，得出什么结论

解题思路：如果在五年内煤厂总数量不变，则每家都翻一番，该地区煤的总产量必定翻一番。

题目里面的信息是，由于技术进步，某个煤矿的人均产量在过去五年翻番，问以上人均产量的信息能得出什么结论？

答案A说，如果这个地区矿工的人数不变的情况下，那么这个地区的媒产量就会翻番。这里的miner是矿工的意思而不是煤矿，煤矿是mine

感觉B不对的主要原因是因果倒置

C加入了文中未提供的信息

一开始想选D，不过觉得它更是support.而且文中也没提供此类信息

E文中没给出此信息

根据排除法就只好选A了，而且A没有什么明显的错误

我觉得B不对的原因在于题目中只说在该地区没有新开的矿，但是没有说每家矿都没有新增工人。因此，虽然该地区总的每工人产量翻一翻，但具体到个别煤矿，总产量的升高有可能是增加了工人的数量导致的。

理解应该这样，三段论，

大前提，如果没有新增的矿场，那么人均生产率增加了一倍，

结论是有个办法使总的生产率提高了。

问的实际上是另一个前提。

即如果有新的矿场，人均生产率会更高---小前提--在这里成为从上文得到的结论。

选C

以上也是争议的原因。要从三段论角度分析。

另外，个体翻番，推整体翻番，太绝对，无论如何不符合GMAT的充分性思想！如果是增加推增加更适合，因此，应该是上文所述的逻辑结构。