One of the differences between Sunni and Shiais in the interpretation of Muhammad's successor, which was the reason for the shism and the emergence of two sects of Islam. The Sunni believed that Muhammad had no real heir and was to be chosen by voting among the people of the Islamic community. So they wanted to choose a close Muhammad's friend, Abu Bakr. Shias believed that the heir should be a successor from Muhammad's family, a relative Ali.
The answer is: A.