Answer:v
Step-by-step explanation:
Given 
Initially spring mass system is moving towards right with velocity 

Now if the spring is released left block moves towards left with a velocity 

As there is no external force applied on the system therefore the change in linear momentum is zero i.e. it is conserved 
so center of mass continue to move towards the right with velocity v or we can say right block moves towards right with velocity 
 and left block moves with velocity
 and left block moves with velocity 
