“Let’s challenge our states to adopt world-class standards,” he said, putting his finger on a huge problem.

“我们要挑战各州（现状），采用世界级的标准，”奥巴马的这句话准确的指出了一个（教育）大弊端。

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It's not the end of the world. - Can't seem to solve that one nagging math problem in class.

看起来一个恼人的数学题无法被解决。

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The second class of problem comes from the world of combinatorics.

第二类问题来自组合数学界。

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"If you throw municipal bonds into disorder, you're going to have a real world-class problem, " Ross was quoted as saying at a luncheon in New York.

FORBES: Magazine Article

Yes, China faces a world-class air quality problem.

FORBES: Magazine Article

The first is a developed world problem, the challenge working-class youth without higher education face finding work in a de-industrialized society.

FORBES: Getting Younger