What is the complete subject of this sentence? The sun is at the center of our solar system?

The complete subject contains the main noun in the sentence; the predicate contains the verb, or action, in the sentence

(202 bc - 220 ad) dynasty started by lui bang; a great and long-lasting rule, it discarded the harsh policies of the qin dynasty and adopted confucian principles; han rulers chose officials who passed the civil service exams rather than birth; it was a time of prosperity

d.)   when the us left nato after the end of the cold war and they had to evolve to focus on more humanitarian measures with the smaller budget