The correct answer is C) they were repeatedly invaded and conquered by Mongol armies from Central Asia.
The other options of the question were A) their leaders, Muslim nobles, forced most Muslims to be serfs. B) Byzantine Christians forced their religion on Muslim people throughout the region. D) western European crusaders conquered the Muslim empires and enslaved most of the people.
Muslim people in the Middle East and other parts of Asia experienced hardship during the time of the European Middle Ages because they were repeatedly invaded and conquered by Mongol armies from Central Asia.
During the Dark Ages in Medieval times, the Mongols had one of the most powerful armies and were known to be fierce warriors that destroyed every town they encountered. After the unification of 1206, the Mongols decided to conquer the Middle East region under the leadership of Genghis Khan.