hat is the MAIN difference between Sunni and Shia Muslims?

Responses
A The Sunni believe in the idea of Monotheism.The Sunni believe in the idea of Monotheism.
B The Shia pray towards Mecca five times every day.The Shia pray towards Mecca five times every day.
C The Shia wanted a family member of Muhammad to succeed him.The Shia wanted a family member of Muhammad to succeed him.
D The Sunni fast from sunrise to sunset during the month of Ramadan.