$A$ circular coil of radius $R$ is carrying a current $I_{1}$ in an anticlockwise sense. $A$ long straight wire is carrying a current $I_{2}$ in the negative direction of the $x$-axis. Both are placed in the same plane and the distance between the centre of the coil and the straight wire is $d$. The magnetic field at the centre of the coil will be zero for the value of $d$ equal to:

• A
  $\frac{\pi}{R}\left(\frac{I_{1}}{I_{2}}\right)$
• B
  $\frac{\pi}{R}\left(\frac{I_{2}}{I_{1}}\right)$
• C
  $\frac{R}{\pi}\left(\frac{I_{2}}{I_{1}}\right)$
• D
  $\frac{R}{\pi}\left(\frac{I_{1}}{I_{2}}\right)$