$(A)$ $\theta=45^{\circ}$
$(B)$ $\theta>45^{\circ}$ and a frictional force acts on the block towards $P$.
$(C)$ $\theta>45^{\circ}$ and a frictional force acts on the block towards $Q$.
$(D)$ $\theta<45^{\circ}$ and a frictional force acts on the block towards $Q$.
f towards $Q, \sin \theta>\cos \theta \Rightarrow \quad \theta>45^{\circ}$
f towards $P, \sin \theta<\cos \theta \Rightarrow \quad \theta<45^{\circ}$


