The current first decreases positively, and the generated magnetic field will also decrease. At this time, according to the right-hand rule, the magnetic field passing through the wire frame is perpendicular to the wire frame and decreases inward, so the current is clockwise. According to the left-handed rule, the ampere force on the left vertical line is greater than that on the right frame, so it is horizontal to the left. When the current decreases to zero and increases in the opposite direction, it can be seen from the right-hand rule that the magnetic field passing through the wire frame increases outward perpendicular to the wire frame, so the current is clockwise. From the left-hand rule, it can be seen that the ampere force on the left vertical frame is smaller than that on the right-hand frame, so it is horizontal to the right. Therefore, A is correct.

So choose: a