Final answer:
Bishop Donatus was a significant figure in religious studies, specifically within Christian schisms. Augustine of Hippo was instrumental in resolving the Donatist controversy. Bishops held influential political and religious roles in Roman governance.
Step-by-step explanation:
Regarding the assessment of Bishop Donatus, the correct statement is b) He was a significant figure in religious studies. Although Donatus himself instigated the Donatist schism within Christianity, the individual who played a pivotal role in ending this split was Augustine of Hippo. Augustine, a critical opponent of the Donatist view and significant figure in religious studies, decisively challenged the Donatists at the 411 Council of Carthage, which eventually led to their expulsion from the church.
Bishops in Roman governance, according to the provided information, played roles that align with option c) They participated in ecumenical councils and dominated local politics. This is evidenced by incidents such as the backlash of Christian populations against pagan figures under the influence of bishops, which shows their capacity to wield political as well as religious power.