The correct answer is A. Reunifying several kingdoms
Explanation:
The Song Dynasty included around nineteen emperors who ruled China from the 10th century to the 13th century. This dynasty is recognized due to its multiple advancements in terms of government and culture. Indeed, during this dynasty, national paper money began to be used as part of the economy and a centralized government was established. This political change unified many kingdoms or territories in China as these were under the rule of the same emperor and share different elements including the use of the same currency.
