d
(d) When the whole system is accelerated towards left then pseudo force (ma) works on a block towards right.

For the condition of equilibrium

\(mg\,\sin \theta = ma\cos \theta \) \(⇒\) \(a = \frac{{g\sin \theta }}{{\cos \theta }}\)

\(\therefore \) Force exerted by the wedge on the block

\(R = mg\cos \theta + ma\sin \theta \)

\(R = mg\cos \theta + m\left( {\frac{{g\sin \theta }}{{\cos \theta }}} \right)\sin \theta \)

\( = \frac{{mg({{\cos }^2}\theta + {{\sin }^2}\theta )}}{{\cos \theta }}\)

\(R = \frac{{mg}}{{\cos \theta }}\)