A sphere is moving in water with a velocity of 1.6 m/s. another sphere of twice the diameter is placed in a wind tunnel and tested with air which is 750 times less dense and 60 times less viscous than water. The velocity of air that will give dynamically similar conditions is
(a) 5 m/s (b) 10m/s
(c) 20 m/s (d) 40 m/s