The bob of a simple pendulum of length $L$ is released at time $t=0$ from a position of small angular displacement. Its linear displacement at time $t$ is given by
(b) $x=a \cos 2 \pi \sqrt{\frac{g}{L}} \times t$
$X=a \sin 2 \pi \sqrt{\frac{L}{g}} \times t$
(c) $X=a \sin \sqrt{\frac{g}{L}} \times t$
(d) $X=a \cos \sqrt{\frac{g}{L}} \times t$