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

the answer is b. i'm positive it's that answer.

because of the importance of consistency in data collection. but we have to evaluate the resource or information, and not just accept what is posted online since information available on the internet is not regulated for quality or accuracy.