B, when the ring falls from the static state, due to the large magnetic flux, induced current appears in the ring, which is affected by ampere resistance. In addition to the three gravities, there is also Ampere force to do work, which leads to the decrease of gravitational potential energy in the process of falling, part of which is used to increase kinetic energy and part of which is used to generate internal energy. Therefore, B is correct;
When the ring falls from the static state, due to the increase of magnetic flux, induced current appears in the ring, which is affected by ampere resistance, so the mechanical energy of the ring is decreasing, so it is wrong.
1. When the ring falls from the static state, due to the large magnetic flux, induced current appears in the ring, which is affected by ampere resistance. From the relationship between force and reaction, we can get the force of the ring on the magnet, which makes the pressure of the magnet on the desktop greater than its own gravity. But when the ring falls into the middle of the rod, it is a mistake, because the magnetic induction line is not cut at those seven moments.
So choose: B.