Learners must be supervised by adults who are at least 21 years old.学员必须由21岁及以上的成年人监督。

ideal for learners非常适合初学者

The grammar guide is a useful aid for language learners and teachers.这本语法指南对语言学习者和教师都很有帮助。

a new aid for younger children or slow learners针对年幼者和学习迟缓者的新教辅手段

She's certainly a quick learner.她确实学得很快。

There is evidence that many learner errors cannot be accounted for in this way.有证据表明学习者的许多错误都不能这样解释。