A metallic ring is dropped down, keeping its plane perpendicular to a constant and horizontal magnetic field. The ring enters the region of magnetic field at t = 0 and completely emerges out at t = T seconds. The current in the ring varies as

During free fall of ring through a magnetic field, when ring enters the constant and horizontal magnetic field, the induced current flows in the ring in such a direction that opposes the cause producing it. Now when ring leaves the magnetic field, again current is induced in the ring but in  opposite direction. Also during the stay of ring completely in the field there is no induction. Hence, correct graph will be (4).