The correct answer is B) Mongols.
Mongols defeated the Pagan kingdom.
Historians consider the Pagan Kingdom as the first form of Empire in the territories of Burma. It started in 849 and ended in 1287. The Pagan Empire saw its last days in the time of emperor Narathihapate, that ruled from 1254 to 1287 when an invasion of the Mongols led by Kublai Khan destroyed part of the empire and the Mongols defeated the Pagans and invaded its territory.