Din't talk with others during the class的同义句如题You ----- ------ with others during the class

Keep silence during the class.
You shouldn't talk with others during the class

Freedom for many children is the coming day when they could improve myself in their own way to use my 24 hours. They can study language by watching film instead of working on boring grammar and multiple choices.
Freedom is as simple as my playing piano all night without worrying about disturbing my 14-year-old neighbour who has to go to school the next day for my house is specially made.
It also could be freedom in my dream that one day, political democracy becomes true. Freedom in my life is the name of all kindness and happiness.
People have common desire under the sun. For mankind, freedom commonly means respect, love, blessing and dignity. For some people, freedom is that some day, he can give up his own interests to guarantee others’ rights. It is no wonder that so many people fought for freedom even didn’t hesitate to give up their lives when necessary .
I would like to be a freedom fighter for human rights some day in future.
环境问题：
The world is not only hungry, it is also thirsty. This may sound strange, since nearly seventy percent of the earth's surface is covered with water. But about ninety percent of this is sea water. Man and most of the animals can only drink and use the remaining percent of water——fresh water.
The need for water is increasing day by day. Only steps are taken to deal with this problem immediately can we avoid a severe world wide water shortage later on. One of the first steps is to develop ways to reuse it.
Experiments have already keen carried out in this field. The used witer has been pumped to a water purifying plant. There, it can be separated from

YOU should not talk with others during the class