D

Step 1: In an inelastic collision between masses A and B, the two masses stick together after the collision. This means they will move as a single body with a common velocity which can be found using conservation of momentum.
Step 2: When masses A and B collide, the total momentum before is equal to the total momentum after the collision.
Step 3: Once blocks A and B combine, they will compress the spring between B and C. Since mass C is initially stationary, the compression in the spring will occur until the system comes to a temporary equilibrium.
Step 4: The maximum compression of the spring occurs when all three blocks move with the same velocity (the velocity of blocks A and B after the collision), at which point the blocks have maximum kinetic interaction, and block C will experience maximum velocity due to the stored spring energy.
Step 5: According to option C, mass C's velocity will be maximum when the spring is undeformed, which is true only during the initial stage before A hits B. After hitting B, spring deformation occurs which results in more interactions.
Step 6: As per option D, stating that C has minimum velocity when the spring is undeformed is incorrect. While the spring is undeformed, that is when mass C has maximum potential to reach maximum velocity just after A collides with B and the spring starts to compress.
Therefore, the incorrect statement is D.