The Ksp values of MA, MB, MC, MD are $1.8\times {10}^{-10},4\times {10}^{-3},4\times {10}^{-8}\&6\times {10}^{-5}$ respectively. If a $0.01\mathrm{M}$ solution of $\mathrm{MX}$ is added dropwise to a mixture containing $\mathrm{A},\mathrm{B},\mathrm{C},\mathrm{D}$ solution the one to be precipitated first will be.

 According to given data, $\left[{\mathrm{M}}^{+}\right]$ needed for precipitation of

$\mathrm{MA}=\frac{1.8\times {10}^{-10}}{{10}^{-2}}=1.8\times {10}^{-8}\mathrm{M}$

$\mathrm{MB}=\frac{4\times {10}^{-3}}{{10}^{-2}}=4\times {10}^{-1}\mathrm{M}$

$\mathrm{MC}=\frac{4\times {10}^{-8}}{{10}^{-2}}=4\times {10}^{-6}\mathrm{M}$

$\mathrm{MD}=\frac{6\times {10}^{-5}}{{10}^{-2}}=6\times {10}^{-3}\mathrm{M}$

So, MA will first precipitate out as it requires lowest concentration of ion.

Therefore, the correct option is (A).