A block is placed on the top of a smooth inclined plane of inclination $\theta$ kept on the floor of a lift.When the lift is descending with a retardation $a$,the block is released.The acceleration of the block relative to the incline is
$\begin{array}{1 1}g\sin \theta\\a\sin \theta\\(g-a)\sin \theta\\(g+a)\sin \theta\end{array}$