Final answer:
The main difference between an ecclesia and a denomination is that ecclesia are state-sponsored and are regarded as an official religion, while denominations are independent from the state.
Step-by-step explanation:
The essential difference between an ecclesia and a denomination is their relationship with the state and their influence on society. Ecclesia are considered state-sponsored and are the recognized official religion within a society, implying a close relationship with the government and a level of influence that affects all aspects of societal operations. On the other hand, denominations are religious organizations that exist independently from the state and have a specific set of practices and beliefs, but they do not represent the official state religion. Examining religious organizations on a continuum of societal influence, we understand that cults have the least influence, while ecclesia have the most. This continuum includes cults, sects, denominations, and ecclesia. Therefore, considering the given options, the correct answer to the main difference between an ecclesia and a denomination is option c, which states that ecclesia are state-sponsored and considered an official religion.