Identify the graph which correctly represents the Moseley's law

According to Moseley's law, square root of frequency of X-ray is plotted against atomic number it gives straight line, the relation is $\sqrt{\mathrm{f}}=\mathrm{c}(\mathrm{Z}-1)$ where $\mathrm{c}=$ constant (for $\sqrt{\mathrm{f}}=0, Z=+\mathrm{c}$, for $\mathrm{Z}=0, \sqrt{\mathrm{f}}=-\mathrm{c}$ ) $\therefore$ Option (b) is correct. as $Z$ can not be negative.