Not long ago, even top college students would likely have had trouble defining sustainability.

VOA: standard.2010.04.22

Students have a lot of trouble with the concepts because there is not much intuition about electromagnetic phenomenon.

学生们对于理解概念,觉得很困难,因为对于电磁学现象,只有很少能凭直觉理解的。

麻省理工公开课 - 媒体、教育、市场课程节选

If Korean students are having trouble with articles, I really recommend they don't get discouraged.

如果韩国学生学习冠词有问题的话，我真地建议他们不要气馁。

韩国人经常犯的失误 - SpeakingMax英语口语达人

I sometimes have trouble with students who talk very softly which is alright in itself and sometimes very sweet.

有时候有些同学说话轻声轻语,这样说话本身没什么,但我却有时听不太明白。

麻省理工公开课 - 电影哲学课程节选