汤丹难选氧化铜矿的选矿是一个世界难题。
The mineral processing of Tangdan refractory copper oxide ores is a worldwide difficult problem.
同年，他的第二本书《世界难题的解决方案》总结了面对人性时的巨大挑战。
That same year, his next book Solutions for the World's Biggest Problems was released, which provided a summary of the greatest challenges facing humanity.
去年十一月份扎克伯格女儿麦柯斯的出生促使这对亿万富豪夫妇捐献出几乎全部财产，用于解决世界难题。
It was Max's birth last November that inspired the billionaire couple to give away nearly all their money to help solve the world's problems.
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