First, you must listen to the teacher carefully, it means less work after class.
首先，你必须认真听老师讲课，这意味着课后作业少了。
Listening to the teacher carefully in class means little work after class.
上课集中注意力听老师讲解意味着课后少花力气。
The teacher did a lot of work inside the class.
老师在班级内部做了许多工作。
The teacher did a lot of work inside the class.
老师在班级内部做了许多工作。
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