In one year she turned from a problem child into a model student.

一年内，她从问题儿童变成了模范学生。

《牛津词典》

Thanks to my English teacher, I turned from a problem child into a model student in just one year.

多亏了我的英语老师，我在一年内从问题儿童变成了模范学生。

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But, in contrast, it is only in modern times that Galileo has become a problem child for historians of science.

但是相比之下，对于科学史家来说，伽利略只是在现代才变成了一个新的难题。

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Often parents don't realize there's a problem because their child does not look fat.

VOA: standard.2010.03.09

And the problem for Freud is premature weaning of a child.

在弗洛伊德看来,问题就出在孩子过早断奶上面。

耶鲁公开课 - 心理学导论课程节选

Sheen has a long history as a problem child and I am not defending either his self-destructive or violent behavior.

FORBES: Charlie Sheen And Public Company Disclosure

You don't want to be seen as a problem child.

FORBES: Magazine Article

The Royal College of Paediatrics and Child Health said obesity was primarily a public health problem not a child protection issue.

BBC: Parental failure over child obesity is 'neglect'