對經濟和民生自不必講。對防疫也有重要作用。從工程學來講，高密度的物質一定向低密度的方向擴散，

來源: 萬湖小舟於 2022-12-08 07:11:04 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

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