Two identical conducting wires $AOB$ and $COD$ are placed at right angles to each other. The wire $AOB$ carries an electric current $I_1$ and $COD$ carries a current $I_2$. The magnetic field at a point lying at a distance $d$ from $O$,in a direction perpendicular to the plane of the wires $AOB$ and $COD$,will be given by

• A
  $\frac{\mu_0}{2\pi d} (I_1^2 + I_2^2)$
• B
  $\frac{\mu_0}{2\pi} \left( \frac{I_1 + I_2}{d} \right)^{\frac{1}{2}}$
• C
  $\frac{\mu_0}{2\pi d} (I_1^2 + I_2^2)^{\frac{1}{2}}$
• D
  $\frac{\mu_0}{2\pi d} (I_1 + I_2)$