What caused the Sunni-Shia split in the 7th Century?
a. The Sunnis believed a Caliph should be elected, but the Shia felt it should be a hereditary position
b. Differences of opinion about what five aspects should make up the pillars of Islam
c. Debate over whether Jerusalem, Medina, or Mecca should be the destination of the Hajj
d. The influence of Persian or Turkish culture on the Muslim community