It’s a measure
because it’s not pointing to a bar line or anything else it’s just on each measure
D. Shadowing
It can't be clustering because that is just putting them carelessly and grouping is different as well
The Catholic church influenced the Medieval Music in the Middle Ages by chanting and preforming by monks but eventually developed a melodic sound which harmonized, actually Catholic Church developed music in a formthat we know today with harmony and melody