Irrespective of the photosensitive material used, the slope of each line should be same, since slope $=\frac{h}{e}$

Since, ${\mathrm{W}}_{\mathrm{A}}>{\mathrm{W}}_{\mathrm{B}}>{\mathrm{W}}_{\mathrm{C}} \Rightarrow {\left({\nu }_0\right)}_{\mathrm{A}}>{\left({\nu }_0\right)}_{\mathrm{B}}>{\left({\nu }_0\right)}_{\mathrm{C}}.$

$\therefore$ a is not possible.

Options (iii) and (iv) are not possible, since the graphs are not parallel.