The answer is a. reunifying several kingdoms.
At the end of Tang Dynasty before Song Dynasty, The country was split into many kingdoms, the emperor of song dynasty also belonged to one of the kingdom. After his rise,he defeated the rest of the kingdoms one by one and finally reunifying the country.
Answer:
C
Explanation:
The 19th-century doctrine or belief that the expansion of the US throughout the American continents was both justified and inevitable.
