One Important Difference Between Islam and Christianity Was That

One important difference between Islam and Christianity was that

A) Islam had extremely formal structures through which the religion spread, while Christianity diffused in a more inconsistent and unpredictable manner.
B) Islam lacked the hierarchical structure that Christianity possessed and spread through more informal channels.
C) Islamic societies encouraged a strict division between matters of religion and matters of state, while Christianity regularly blended the two together.
D) Islam relied on an educated elite to spread the teachings of the Quran, while Christianity made regular use of merchant missionaries to spread the teachings of the New Testament.