"Being more socially engaged in your community - maybe in environments which aren't always just the same, a little bit more challenging socially - may be a very good thing.

VOA: standard.2010.07.14

In any case, whatever one makes of those examples, Machiavelli seems to be challenging important aspects of the classical conceptions that we've been talking about up to this point.

不管人们如何理解这些例子，马基雅维利似乎正在挑战,我们至此一直在讨论着的古典概念的,重要方面。

耶鲁公开课 - 政治哲学导论课程节选

because school can be really challenging and stressful,

因为学校的学习很有挑战性也很有压力，

百慕大出身 - SpeakingMax英语口语达人

"We don't want to be rebels and betray our families, but we do want to leave home and do interesting and challenging things that maybe our families don't understand because they are still stuck in the old world a little bit.'" In the novel,Gabi faces another dilemma.

VOA: standard.2010.07.22

I think this is as good list so let's go and think about what might be a little bit more challenging.

我想上面这些都是很好的例子,接下来我们思考一些更有挑战的问题

耶鲁公开课 - 生物医学工程探索课程节选

We're going to really get into this next class, but I just want to introduce it to you to give us a start, and many of you have used Lewis structures in high school, but we'll be doing some much more challenging Lewis structures, I can assure you, in this class here.

其实我们下节课才会详细介绍它，但是今天我只想以简单介绍作为开始，大部分同学在高中就用过路易斯结构了，但是我们会遇到一些更具挑战性的,路易斯结构，我可以向大家保证，在这门课中会的。

麻省理工公开课 - 化学原理课程节选

It can be very, very challenging.

这非常非常具有挑战性。

伦敦的出租车司机 - SpeakingMax英语口语达人