c
For wheatstone bridge,
It is independent of emf Let $r=K R$
$\Rightarrow \mathrm{r}_{1} \mathrm{r}_{4}=\mathrm{K}^{2}\left(\mathrm{R}_{1} \mathrm{R}_{4}\right)=\mathrm{K}^{2}\left(\mathrm{R}_{2} \mathrm{R}_{3}\right)=\mathrm{r}_{2} \mathrm{r}_{3}$
So it is still balance Even if battery and galvanometer are interchanged, still it is balanced. $(1)$ $(3),$ $(4)$ are true, hence.