Then, let's look at the abdication system in item A, which is a way for China to recommend the leader or emperor of a tribal alliance to give way to others in ancient times, that is, each tribe decides by majority vote. The era of Yao, Shun and Yu ended with the son of Yu.
Item B enfeoffment system refers to the Zhou Dynasty, especially the Western Zhou Dynasty, where the king enfeoffed the land to three kinds of people: royalty, heroes and descendants of ancient emperors.
Item D: The unification of Emperor Wu of the Han Dynasty (it should be unified, not unified) refers to the promulgation of the "Grace Act" and the attached benefit law by Liu Che, which further weakened the power of the kingdom and strengthened the central government's control over the localities; Five baht unified casting; Accept Dong Zhongshu's suggestion of "ousting a hundred schools of thought and respecting Confucianism alone", regard Confucianism as the orthodox thought of feudal rule, and exclude other schools (Confucianism became the orthodox thought of China's feudal rule for more than two thousand years from now on) ... to realize the great unity of politics, economy and culture and consolidate the Western Han regime.
From this point of view, there is only C.