The velocity of sound in a fluid is given as

where B is the bulk modulus and ρ is the density of the fluid.

It is clear from the relation that if B increases V also increases but when ρ increases V

decreases. Since B and ρ are both greater than air for water, B increases V but ρ decreases V

for water. So until the ratio, B/ρ is available for both the water and air the velocity of sound in

these mediums cannot be compared. Hence, only option D is correct.