-At a time - is more time-specific and pin- pointing a narrow point of time, A person' s life isn't rightly measurable in such constricted sense.- During a time - gives a broader time frame and is logically, if not grammatically, preferable
To Daagh, since you picked C:
if you remove the non-restrictive clause you get:Typically
, during a time when women had a narrow range of choices, Mary Baker Eddy became a distinguished writer and the founder, architect, and builder of a growing church.
Which doesn't make sense, does it?
Therefore D. No need to wait for OA here.
I will greatly appreciate your KUDOS my friends!