I would def put c cause they both sound about right
Generally,the vitrage,or stained glass technique was used to convey an idea of other worldliness. When a person would enter the cathedral,the light would shine through the windows and illuminate the interior,causing a colourful ambient that would leave the person feeling as though they had entered another world;the world of God. The principle in the Byzantine age was the same,except it was more so to signify the god like attributes of the rulers themselves.
He undertook a study of it :)
