求助，GWD01-14

zhulisky4444

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?

A.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.

B.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.

C.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.

D.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.

In Tribnia the cost of producing a given quantity of coal has declined over the past five years.
题干后面有个even though,那意思不是说要是新建了miner的话，就不止double 了吗？我只打A是正确的叙述，但我觉得加了even though后他想表达的就是C的意思啊~~~求助各位啊！

sdcar2010

A is correct and C might not be correct.

If a new mine is opened, the initial output per miner might be lower than the current level since it is a NEW mine and we know nothing about the efficiency of operating a new mine!

This is a must be true type of question and A) must be true according to the passage.