Answer:
Correct answer is C) How the successors should be chosen
Explanation:
A is wrong because all the rulers after Muhammad used the title caliphs.
B is also wrong because the successors were changing the capital according to the needs of the country.
C is correct because some believed that the ruler should be chosen by the leaders, and some believed that the rulers should by relatives of Muhammad.
D is not correct also, as the conquest was not an issue. It was important to spread the country, it wasn't important in which direction.