The correct answer is B) both religious groups often tried to force conversion.
What describes a similarity between the ways in which the Islamic caliphates and Christian states dealt with conquered territories during the postclassical era is that both religious groups often tried to force conversion.
Most of the territories in those years were conquered and the religious beliefs spread in those territories through trade, missionaries and event pilgrimage in some cases. In the case of Islam or Christianity, one of the goals in the new territories was to teach the religion to the people. And in most cases, more than teaching, they tried to force conversion although many times people renegade and did not easily accept the teachings.
