Who was the first person to designate pitches and write them down on a staff? hildegard von bingen the troubadour attila guido d'arezzo?

The answer is Guido D'Arezzo. He was the creator of the modern staff, he had used yellow and red lines to indicate pitches in the staff. In the modern era, these yellow and red lines were removed but still followed D'Arezzo's modern musical staff. Aside from the musical notation, D'Arezzo is also known for his text called "Micrologus"