Question

Over which main point did Sunnis and Shias disagree?

Answer 1

C. who should be Muhammad's successor

Explanation:

The two sects disagree over who should be the Khalifa and by extension the ruler of the caliphate after the death of prophet Muhammad. The Sunnis were the ones that lobbied for the four consecutive Khalifas starting with Abu Bakr while the Shias firmly advocated for Ali ibn e Talib.

This case was the real divide that formed the two most important sects of Islam which is the Sunni and the shia.