$10m$ is the total mass of a cannon that includes all shells. Initially, the cannon is moving with a velocity of $10 \ m/s$ along a horizontal frictionless path. If the cannon fires $n$ shells of mass $m$ in the direction of motion of the cannon one by one with velocity $u$ with respect to the ground, which of the following statements is correct? (Neglect any friction force)

• A
  If $u > 10$, after some shots $(n > 1)$, the velocity of the cannon may become $u$.
• B
  If $u < 10$, after some shots $(n > 1)$, the velocity of the cannon may become $u$.
• C
  If $u = 10$, after some shots $(n > 1)$, the velocity of the cannon may become $u$.
• D
  For any speed $u$ and any number of shots, the cannon speed cannot be $u$.