Both $\mathrm{N}\mathrm{a}\mathrm{C}\mathrm{l}$ and $\mathrm{K}\mathrm{C}\mathrm{l}$ are strong electrolytes and as $\text{N}{\text{a}}^{+}$ (aq) has less conductance than ${\mathrm{K}}^{+}$ (aq) due to more hydration of $\text{N}{\text{a}}^{+}$ (g) due to small size and more hydration energy therefore the graph of option (B) is correct here.
Extent of hydration $\propto \frac{1}{{\mathrm{\Lambda }}_{\mathrm{m}}}$