Explanation

(a) Time period of a simple pendulum of length $l$ is given by
$T = 2\pi\sqrt{\frac{l}{g}}$
where $g$ is acceleration due to gravity.
On moon
$g_{m} = \frac{g}{6}$
$\therefore$ $T^{'} = 2\pi\sqrt{\frac{l}{\frac{g}{6}}} = 2\pi\sqrt{\frac{6l}{g}} = \sqrt{6}.2\pi\sqrt{\frac{l}{g}}$
$\Rightarrow$ $T^{'} = \sqrt{6}T$
Hence, time period increases on the surface of moon.