A teacher can usually tell if students are listening by looking at their body language. If students are making eye contact, nodding, or sitting up straight, it shows they are paying attention. On the other hand, if they are playing with their phones or talking to their friends, it's clear they are not really listening.
老师通常可以通过观察学生的肢体语言来判断他们是否在听讲。如果学生保持眼神交流、点头或坐得端正,说明他们在认真听讲。另一方面,如果他们玩手机或与朋友交谈,就很明显他们并没有真正听讲。