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1·In itself, it's not a difficult problem to solve.

这本身并不是个难解决的问题。《牛津词典》

2·How to improve the quality of products was a difficult problem to him.

如何提高产品质量对他来说可是个难题。

3·Extracting heat from very hot, dry rocks presents a more difficult problem: the rocks must be fractured to permit the circulation of water, and the water must be provided artificially.

从极热的而干燥的岩石中提取热量，暴露出了一个更加困难的问题：必须击碎岩石以保证水的循环，而水必须是人工提供的。

4·She is working at a difficult problem in mathematics.

她在做一道数学难题。《新英汉大辞典》

5·It's really a difficult problem.

这真是个难题。

6·At first there was a seemingly difficult problem.

在开始的时候存在一个难题。

7·Never have I come across such a difficult problem.

我还从没有遇到过这样困难的问题。

8·He soon turned his attention to the difficult problem.

他很快把注意力转到这个难题上。

9·The greatest scholar cannot solve this difficult problem.

再伟大的学者也没有办法解答这个难题吧。

10·Fortunately, it's not a difficult problem (see Listing 6) to fix.

所幸的是，这个问题不难解决(见清单6)。

难题

1·How to improve the quality of products was a difficult problem to him.

如何提高产品质量对他来说可是个难题。

2·She is working at a difficult problem in mathematics.

她在做一道数学难题。《新英汉大辞典》

3·Even though these economies are only just starting to feel the upturn, policymakers now face a difficult problem: how to sustain a robust recovery without blowing up bubbles.

尽管这些经济体的经济刚开始好转，但政策制定者现在面临难题：在避免经济泡沫的情况下如何保持经济的强劲反弹。

4·He soon turned his attention to the difficult problem.

他很快把注意力转到这个难题上。

5·Providing dynamic internationalization of information for display is a difficult problem.

为显示提供信息的动态国际化是一个难题。