Answer
(a) location 1, upward; location 2, zero; location 3, upward
(b) III
Work Step by Step
(a) We know that at location (1), the ring enters the field and the induced current should oppose the field by creating an induced magnetic field. As the induced magnetic field opposes the ring, thus it is in an upward direction.
At location (2), the ring is in the uniform magnetic field, hence the magnetic force is zero.
At location (3), the ring leaves the field and the induced current should oppose the field by creating an induced magnetic field. Thus, the magnetic force is in the upward direction.
(b) We know that the best explanation is option (III) -- that is: upward at 1 to oppose entering the field; zero at 2 because the field is uniform; and upward at 3 to oppose leaving the field.
