Explanation

(d) Variation of different variables $(Q\ ,\ C,\ V,\ E\ and\ U)$ of parallel plate capacitor when dielectric ($K$) is introduced when battery is removed is
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ C^{'} = \ KC\ E^{'} = E/\ K$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ Q^{'} = \ QU^{'}\ \ \ = U/K$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ V^{'} = \ V/K$