A sound producing body is at considerable distance from a man. There can be four different media W, X, Y and Z between the sound producing body and the man. The medium X brings the sound to man most quickly whereas medium Z takes the maximum time. The time taken by medium W in bringing sound to man is less than that of X but more than that of Z. The medium Y, however, fails to bring the sound from the sound producing body to the man. Which medium could be the one :
(a) having a fixed shape and no fixed volume ?
(b) having a fixed volume but no fixed volume ?
(c) having the same composition as that on the moon ?
(d) having a fixed shape and a fixed volume ?