A particle P moving with speed v undergoes a head -on elastic collision with another particle Q of identical mass but at rest. After the collision the collision
A. Both P and Q move forward with speed `(v)/(2)`
B. Both P and Q move forward with speed `(v)/(sqrt(2))`
C. P comes of rest and Q moves forward with speed v
D. P and Q move in opposite direction with speed `(v)/(sqrt(2))`.