A shell is fired from a connot with a velocity V at an angle 0 with the horizontal direction .At the highest point in its path it explodes into two pieces of equal masses. One of the pieces retraces its path to the cannon.The speed of the other piece immediately after the explosion is :
A. `3V cos 0`
B. `2V cos 0`
C. `3/2Vcos 0`
D. `V cos 0`