Answer:
The correct answer is d) Pope Gregory the Great was the first composer of this genre of sacred music, writing so many that it was named after him.
Explanation:
Gregorian chants are monophonic, unaccompanied sacred songs in Latin within the Catholic Church tradition. This liturgy form was developed in Europe during the 9th and 10th centuries.
Although this tradition was named after the Pope Gregory i, and some have attributed him the invention of this chant, more recent studies have pointed out that it might have arisen from the synthesis of Roman and Galician chants during the Carolingian dynasty (Frankish).