Sufism became popular during the thirteenth-century Mongol invasions because:
A) many Muslims admired the self-sacrifice of Al-Husayn ibn Manur al-Hallaj.
B) the Mongols supported the sect after being converted by Sufi missionaries.
C) many Muslims sought spiritual solace in the midst of destruction and hardship.
D) Byzantium took advantage of the invasions to attack Sunnites and Shi'ites.