Where Was the First Major Christian Church Council Held and What

Where was the first major Christian Church council held and what was the result of the meeting?

A) Hippo, where St. Augustine became bishop.
B) Nicaea, where a number of theological questions were settled.
C) Rome, where the doctrine of Petrine Succession was adopted.
D) Constantinople, where clergy and lay people studied many ancient documents.
E) Milan, where Church officials decided to make Rome their official headquarters.