$A$ galvanometer of resistance $G$ is connected in a circuit. Now,a resistance $R$ is connected in series with the galvanometer. To keep the main current in the circuit unchanged,the resistance $S$ to be put in parallel with the series combination of $G$ and $R$ is:

• A
  $\frac{G^2}{R} + G$
• B
  $\frac{R^2}{G} + G$
• C
  $\frac{G^2}{R} - G$
• D
  $\frac{R^2}{G} - G$