In the experimental set up of metre bridge shown in the figure, the null point is obtained at a distance of 40 cm from A. If a $$10\Omega$$ resistor is connected in series with $$R_1$$, the null point shifts by 10 cm. The resistance that should be connected in parallel with $$(R_1 + 10)\Omega$$ such that the null point shifts back to its initial position is

A

$$20\Omega$$

B

$$40\Omega$$

C

$$60\Omega$$

D

$$30\Omega$$