A block of mass M is resting on an inclined plane shown in fig. The inclination of the plane to the horizontal is gradually increased . It is found that when the angle of inclination is $\theta$ the block just begins to the slide down the plane. What is the minimum force F applied parallel to the plane that would just make the block move up the plane ?

Question

$\begin{array}{1 1} Mg\;\sin \theta \\ Mg\;cos \theta \\ 2\;Mg\;\cos \theta \\ 2\;Mg\;\sin \theta \end{array}$