The researchers theorized that dating violence was just one of several problem behaviors - such as weapon carrying, academic difficulty and substance abuse - that occur together in teenagers.

研究人员从理论上推断恋爱暴力行为只是青少年身上集中出现的几种问题行为之一，比如，携带武器、学业困难及滥用药物等。

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And the difficulty was basically the problem of duplication.

提出了一个难题，这难题就基于复制。

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So as you can see, as we escalate the problem difficulty, the difference between the good method and the not quite as good method gets bigger and bigger and bigger.

如你所见，当我们处理更复杂的,问题的时候，优良的算法,和并不那么好的算法之间的,差异会变的越来越大，这一点很重要。

麻省理工公开课 - 计算机科学及编程导论课程节选

And the difficulty was basically the problem of duplication.

提出了一个难题，这难题就基于复制。

耶鲁公开课 - 死亡课程节选

In Healy's opinion, electronic gaming at a young age can lead to shorter attention spans, a lack of internal motivation, difficulty with problem solving and a lack of creativity.

FORBES: Baby Frankenstein

Manpower was the real problem, and in particular the difficulty of persuading engineers and skilled tradesmen to leave the United States to dig a ditch in a fetid tropical swamp.

ECONOMIST: American canal building

As a non-mathematician, he appreciates the difficulty of explaining a recondite mathematical problem to a general audience, and gives a vivid account both of the passion that mathematicians have for their subject and of the fascination for this particular problem.

ECONOMIST: Mathematics