1) Geographic features like mountains and deserts isolated parts of China and affected development, while resources like coal and iron attracted foreign trade and imperialism.
2) Confucianism encouraged harmony and filial piety, while Legalism saw order through strict laws; these philosophies influenced Chinese society.
3) The Opium War marked China's decline as European powers imposed unequal treaties and took territories, starting the "Century of Humiliation" and weakening China.