C, is the answer. The key "how it was made" pretty much just state the word process.
I think the answer is 'purity' as it makes the most sense. Purity is represented by the color white, while green is either jealousy or happy/calming(rebirth). New ideas can be symbolized by green, as in a green flag or a green light.
The answer is : staff lines. He devised an arrangement of lines and spaces that developed into the musical staff. Two of Guido D'Arezzo's primary contributions to music history
: 1. developed a 4-line staff circa. 1025
2. wrote a text on music ca. 1026 called "Micrologus"
