Which statement best describes a difference between China before the Mongol invasion and after the Mongol invasion?

A. Before the Mongol invasion, Chinese territories were all part of a larger empire. After the invasion, the Mongols separated them into independent kingdoms.
B. Before the Mongol invasion, China allowed foreigners to serve in its government. After the invasion, only native Chinese could become officials.
C. Before the Mongol invasion, Chinese officials were selected through civil service exams. After the invasion, this system was eliminated.
D. Before the Mongol invasion, China’s government practiced religious tolerance. After the invasion, only Mongol religions could be practiced