In history we are making abc's of the founding documents you figure out a word that goes with each letter of the alphabet like c for constitution or o for oath but i can't figure something out for z?

Which was the original difference between sunnis and shias? a. they disagreed on the content of the five pillars. b. they disagreed on the role of sharia in muslim society. c. they disagreed on the role of imams in the islamic religion. d. they disagreed on who should have succeeded muhammad.