“德意志民族曾经号称‘思想家和诗人的民族’，也涌现出了一流的科学家和艺术家。……但是，这个伟大的民族有曾在一个狂人的操纵下进行过最骇人听闻的大屠杀。”后者产生的历史根源是

根据短文内容回答下列问题。

    A poor farmer had a friend who was famous for the wonderful apple trees he grew.

    One day, his friend gave the farmer a young apple tree and told him to plant it. The farmer was pleased with the gift, but he did not know where to plant it.

    He was afraid that if he planted the tree near the road, strangers would steal the fruit. If he planted the tree in one of his fields, his neighbours would come at night and steal some of the apples. If he planted the tree near his house, his children would take the fruit. Finally he planted the tree in his woods. But without sunlight and good soil(土壤), the tree soon died.

    Later the friend asked the farmer why he had planted the tree in such a poor place. "What's the difference?" the farmer said angrily and then told what he had thought.

    "Yes, "said the friend, "but at least someone could have enjoyed the fruit. Now you not only have robbed everyone of the fruit, but also you have destroyed(毁掉) a good apple tree!"

读最佳人口规模示意图，回答下列问题。