b
\(\mathrm{AgCl} \rightleftharpoons \mathrm{Ag}^{+}+\mathrm{Cl}^{-}\)

\(\mathrm{Ag}^{+}\) is \(\mathrm{S}\)

\(\mathrm{Cl}^{-}\) is \(0.1\)

\(\mathrm{K}_{\mathrm{sp}}=\left[\mathrm{Ag}^{+}\right]\left[\mathrm{Cl}^{-}\right]\)

\(1.6 \times 10^{-10}=S \times 0.1\)

\(1.6 \times 10^{-9}=S\)