Hello!
Theodora was an empress, whose husband was the Emperor of the Byzantine Empire.
That makes answer D. [Empress of the Byzantine Empire] an unlogical answer since she only helped advance the Empire alongside her husband.
Answer B. [Roman mosaic artist] is also incorrect.
It was said that for a time, she made her living as a wool spinner.
So, she did not have time to become an actual artist.
This answer often is mistaken to be correct because she was represented in a mosaic portrait in the Church of San Vitale in Ravenna.
Answer C. [Architect of the Hagia Sophia] is incorrect.
because it was directed under the direction of the Byzantine emperor Justinian I, her husband.
Your correct answer is A. [Protest leader in the Nika Rebellion]
Hope this helps!