如图分别表示人体免疫的两种免疫过程，结合图示分析下列说法正确的是（   ）

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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。故天将降大任于斯人也，必先苦其心志，劳其筋骨，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，而死于安乐也。

    Most American families are smaller than the families in other countries. Children in the USA will leave their parents when they grow up. They usually live far from their parents because they want to find good jobs. They often write to their parents or telephone them. And they often go to visit their parents on holidays.

    Parents usually let their children choose their own jobs. Americans think it is important(重要的) for them to make decisions(作决定).

    Children are also asked to do some housework at home. And in many families，children will get money from their parents for doing some housework. Because American parents want to let their children learn how to make money for their own use.