The solubility product of $\mathrm{AgCl}$ is $1.8\times {10}^{-10}$. Precipitation of $\mathrm{AgCl}$ will occur only when equal volumes of solutions of:

${\mathrm{ppt}}^n$ occurs when $k_{ip}>k_{sp}$. For each option,

$\text{ (a) }\left[k_{ip}=\frac{{10}^{-8}}{4}>k_{sp}\right]$                         

 $\text{ (b) }\left[k_{ip}=\frac{{10}^{-14}}{4}<k_{sp}\right]$

$\text{ (c) }\left[k_{ip}=\frac{{10}^{-10}}{4}<k_{sp}\right]$                      

    $\text{ (d) }\left[k_{ip}={10}^{-10}<k_{sp}\right]$

Thus, precipitation of $\mathrm{AgCl}$ will occur only when equal volumes of solutions of ${10}^{-4}\mathrm{M}{\mathrm{Ag}}^{+}$ and ${10}^{-4}{\mathrm{MCl}}^{-}$ are mixed.