A. When the ring falls from rest, the magnetic flux becomes larger, causing an induced current in the ring and ampere resistance, so the mechanical energy of the ring is not conserved. Therefore, A is wrong;
B. When the ring falls from rest, the magnetic flux becomes larger, causing an induced current in the ring, which is subject to ampere resistance. In addition to the work of 3 gravity, there is also work of ampere force. , causing the gravitational potential energy to decrease during the falling process, part of it is used to increase kinetic energy, and part of it is used to generate internal energy. Therefore, B is correct;
In the middle, when the ring falls from rest, the magnetic flux becomes larger, causing an induced current in the ring, which is subject to ampere resistance, so the mechanical energy of the ring is decreasing. Therefore, there is an error;
1. When the ring falls from rest, the magnetic flux increases, causing an induced current in the ring, which is subject to ampere resistance. From the relationship between the action force and the reaction force, we can get the force the ring exerts on the magnet, which makes the pressure of the magnet on the tabletop greater than its own gravity. However, when the ring falls into the middle of the rod, it is because the magnetic field lines are not cut at those seven moments. So there is an error;
So choose: B