43. Two identical parallel conducting rings have a common axis and are separated by a distance a, as shown. The two rings each carry a current I, but in opposite directions. At point P , the center of the ring on the left the magnetic field due to these currents is
(A) zero
(B) in the plane perpendicular to the x -axis
(C) directed in the positive x-direction
(D) directed in the negative x -direction
