What is a “blues scale”?

a. a five-note scale found often in folk music and non-Western music
b. a seven-note scale in which the third, fifth, and seventh pitches are sometimes flat, sometimes natural, and
sometimes in between
c. a six-note scale wherein each pitch is a whole tone away from the next
d. a musical process in which all of the scales move in the same direction, and at the same intervals, for a period
of time
e. a seven-note scale that suggests melancholy emotions

ANSWER: b