Why did christians choose to illustrate their teachings in their architecture

By the beginning of the fourth century Christianity was a growing mystery religion in the cities of the Roman world. It was attracting converts from different social levels. Christian theology and art was enriched through the cultural interaction with the Greco-Roman world. But Christianity would be radically transformed through the actions of a single man.

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.