or $\quad \alpha=\frac{10^{-3}}{0.1}=10^{-2}$
$K a=C \alpha^{2}=0.1 \times 10^{-2} \times 10^{-2}$
$=10^{-5}$
$A = NH_4Cl$; $ B = CH_3COONa$; $ C = NH_4OH$; $D = CH_3COOH$