An object is kept on a smooth inclined plane of 1 in $l$. The horizontal acceleration to be imparted to the inclined plane so that the object is stationary relative to the inclined is
(a) $g \sqrt{l^{2}-1}$
(b) $g\left(l^{2}-1\right)$
(c) $\frac{g}{\sqrt{p^{2}}}$
(d) $\frac{g}{l^{2}-1}$