题目选项分析

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?

【选项】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.