In figure, two long parallel wires carry equal currents in opposite directions. Point O is situated midway between the wires . X-Y plane contains the two wires and the  Z-axis comes normally out of the plane of paper. P is a point such that the magnetic field B at P is zero . Then P lies 

• A

  Anywhere on YZ plane

• B

  Anywhere on X-axis

• C

  Anywhere on Y-axis

• D

  $\mathrm{Anywhere} \mathrm{on} \mathrm{Z}-\mathrm{axis}$