In What Way Did Muhammad's Position in Medina Become a Model

In what way did Muhammad's position in Medina become a model for Islamic governance?

A) Muhammad's political position in the community made Medina's political and religious institutions inseparable.
B) Muhammad established the tradition of doctrinal disputes being settled by a supreme leader, later referred to as the imam.
C) Muhammad resolved all conflict via diplomacy and debate and never through war.
D) Muhammad discouraged Muslims from having any contact with nonbelievers due to fears of spiritual contamination.