The brick maker treadles over clay to pick out the stones.

粘土上踏动踏板，以便捡出其中的石块。

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For example, one thing that could happen is that you build it up with wood and clay, you pick the wrong material for a bridge, and it will not stand up to the forces of nature.

例如,其中的一个问题是,选择了木头和粘土作为造桥的材料,你就选错了材料,这座桥难以与自然力相抗衡

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