What causes sound

waveforms

dust particles

vibrating molecules

either A or C

Explanation:

soft,hard and rough for soft would be a pillow or a stuffed animal hard wood floor or a table rough paint

including the octave, the answer would 8 notes in a major scale with one note being played twice. ex) c major scale includes: c, d, e, f, g, a, b, c

notice that c is played twice

however, if you were to ask me how many different notes are in a major scale- the answer would be 7.