我们可以用（   ）方法把食盐从水中分离出来。

  The students were having their chemistry（化学）class. Miss Li was telling the children what water was like. After that, she asked her students, “What's water?" No one spoke for a few minutes．Miss Li asked again，“Why don't you answer my question？Didn't I tell you what water is like？”
Just then a boy put up his hand and said，"Miss Li，you told us that water has no color and no smell．But where to find such kind of water？The water in the river behind my house is always black and it has a bad smell．"Most of the children agreed With him．
“I'm sorry，children．”said the teacher，"Our water is getting dirtier and dirtier．That's a problem”．

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生于忧患，死于安乐

       舜发于畎亩之中，傅说举于版筑之间，胶鬲举于鱼盐之中，管夷吾举于士，孙叔敖举于海，百里奚举于市，故天将降大任于是人也，必先苦其心志，劳其筋骨，饿其体肤，空乏其身，行拂乱其所为，所以动心忍性，曾益其所不能。

       人恒过然后能改，困于心衡于虑而后作，征于色发于声而后喻。入则无法家拂士，出则无敌国外患者，国恒亡，然后知生于忧患，死于安乐。