c
For total internal reflection on face \(AC\)

\(0>\) critical angle \((C)\) and \(\sin \theta \geq \sin C\)

\(\sin \theta \geq \frac{1}{w_{\mu _g}}\)

\(\sin \theta  \geqslant \frac{{{\mu _w}}}{{{\mu _g}}}\) \( \Rightarrow \sin \theta  \geqslant \frac{{\frac{4}{3}}}{{\frac{3}{2}}}\)

\(\therefore \sin \theta \geq \frac{8}{9}\)