Water is flowing through a horizontal tube of non - uniform cross - section. At a place the radius of the tube is 1.0 cm and the velocity of water is 2 m/s. Then, what will be the velocity of water at a point where the radius of the pipe is 2.0 cm?
A. 1 m/s
B. 0.25 m/s
C. 20 m/s
D. 0.5 m/s