困难问题：指具有挑战性、复杂性或难以解决的问题。
难题；难问题-引用次数：1
参考来源高效磨削的瓶颈与对策
... difficult position艰难的境况 difficult problem困难的问题 difficult sound难发的音 ...
难点问题
In itself, it's not a difficult problem to solve.
这本身并不是个难解决的问题。
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。
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。
She began to explain to the students how to solve a very difficult problem.
VOA : special.2009.10.25
It's a difficult problem that not everyone is smart -they vary in their ability -so we try to make a world in which it's pretty safe for the small investor who's not paying attention.
不是所有人都是聪明人,这是个难题,大家能力不同,所以我们试图营造一个环境,一个让小投资者感到安全的环境,而无需忧心忡忡
金融市场课程节选 : 耶鲁公开课
It shouldn't be difficult to see a kind of problem that is beginning to arise in Milton's text here.
这是一个很容易看出的问题,在弥尔顿的作品中也被提了出来。
弥尔顿课程节选 : 耶鲁公开课
She was never willing to leave a problem unfinished, even difficult problems in mathematics.
VOA : special.2009.11.08
Hobrooke admits is a very complicated and difficult problem to address.
VOA : standard.2009.06.15
Brazile recalled this as the precise moment when she knew Daley could tackle any difficult problem.
Conservative councillor John Knapman said it was a "difficult problem at this time of year".
But overall, diabetes, driven so intensely by overweight and obesity, "is a terribly difficult problem, " Dr. Weir says.