Final answer:
Bishop Donatus's reaction to Emperor Constantine was hostile, as he opposed Constantine's efforts to exert control over the church.
Step-by-step explanation:
Bishop Donatus's reaction to Emperor Constantine can be described as hostile.
Donatus was the leader of a schismatic group known as the Donatists, who opposed the way Christianity was being practiced under the Roman government. Constantine sought to unify Christianity and suppress the Donatists, which led to Donatus and his followers facing persecution and exile.
This demonstrates that Donatus had a hostile reaction towards Constantine's efforts to exert control over the church.