in class指课堂课
in the class 意思班级面班
in classes
In English classes, body language has functions of organizing, demonstrating and suggesting.
体态语英语教组织、示范、暗示作用
Do volunteer work, take up a hobby, enroll in classes or pursue a part-time job.
做些志愿工作培养点兴趣参加些课程点东西或干点兼职工作
in class 是个成语,所以不用冠词。意思是:课堂上。