The total kinetic energy of the cannon and cannonball system will remain the same.
When a cannon is fired, the potential energy from the explosive blast is converted into kinetic energy of both the cannon and the cannonball. If the energy of the blast remains constant, it will still be distributed between the cannon and the cannonball, regardless of the mass of the cannon.
As the mass of the cannon increases, more of the blast energy goes into moving the cannon, which means less energy is available to be converted into the kinetic energy of the cannonball. However, the total kinetic energy of the entire system (cannon plus cannonball) will equal the initial energy from the blast, which remains constant.
So the correct answer is: The total kinetic energy remains the same.