The clergy were the religious people of the Middle Ages. Following the pope, in order of rank, there were bishops, priests, monks and nuns. In the latter part of the Middle Ages, the pope, as head of the church, had much influence over the king and total control of the clergy.
The correct answer is religious persecution and here's why:
The Mongol rule occurred at the same time but was not as important as religious persecution. Muslim rule was common earlier during the 6th century, while intellectual oppression was not a recurring issue.
