In the classroom， sometimes it is noisy and sometimes it is silent. Why? Just because of "teacher".
If the teacher didn't come， the students wouldn't study hard at all， some were passing notes， some were tearing off the paper in the workbook and folding the airplane to play， some were secretly sitting down and moving the chairs to other places， and some went too far， and went to the podium to play with the chalk newly bought by the teacher， even if the class cadres went up to manage the order， it would be useless. Of course， there will always be students who love to snitch and report to the class teacher. Those naughty students have been criticized by the teacher several times， but they are not to be outdone. This time， they vowed to study hard in the future， and may do it again next time.
If the teacher's footsteps are heard at the door， the students sitting by the window will give an "ok" gesture， which is a good secret code colluded with the naughty boy， representing "the teacher is coming". At this time， the naughty boys pretended to study hard. The teacher came in， looked at the students who were doing their homework carefully， and nodded with satisfaction.
This is why the classroom is sometimes noisy and sometimes silent. Are you satisfied?教室里，有时喧闹无比，有时寂静无声，这是为什么呢？只是因为“老师”。