c
Let the potential of common point is $\mathrm{O}$ and potential of all other points are as shown in figure
$\frac{x-10}{10}+\frac{x+6}{20}+\frac{x}{10}+\frac{x-10}{5}=0$
$\Rightarrow \mathrm{x}=6 \mathrm{\,V} \quad \therefore 1_{20\, \Omega}=\frac{6+6}{20}=0.6 \mathrm{\,A}$
