Pythagoras discovered by stretching out two strings that to create interval of a you need to play the second string using a ratio of 2:1. A. perfect unison
B. perfect fourth
C. perfect octave
D. perfect fifth.

C.perfect octave

Explanation:

Pythagoras studied the Greek instrument known as the Lyre to find the different sounds produced when you change the length of the strings. He discovered that if the strings are of the same length they produced the same sound but if they were of different lengths they produced different sounds.

If the two strings length are in ratio 1:1 they have the same sound known as perfect unison, if the two strings are in ratio 2:1 the sound is a perfect octave, if two strings length are in ratio 3:2 the sound is a perfect fifth

i think it’s true but i’m not sure

c. the branch of philosophy that deals with beauty and how it is expressed and appreciated