`ABCDE` is a smooth iron track in the vertical plane. The sections `ABC` and `CDE` are quarter circles. Points `B` and `D` are very close to `C.M` is a small magnet of mass `m`. The force of attraction between `M` and the track is `F`, which is constant and always normal to the track. `M` starts from rest at `A`, then:
A. If M is not to leave the track at C then `F ge 2mg`
B. At B, the normal reaction of the track is `F - 2mg`
C. At D, the normal reaction of the track is `F + 2mg`
D. The normal reaction of the track is equal to F at some point between A and C
