Explanation

(c)
Pure hydrogen peroxide is an unstable liquid and decomposes into water and oxygen either upon standing or heating.
$2H_{2}O_{2} \rightarrow 2H_{2}O + O_{2};\ \ \ \ \ \ \ \ \ \ \ \ \mathrm{\Delta}H = - 196.0\ kJ$
To prevent decomposition of $H_{2}O_{2},$ phosphoric acid, acetanilide or glycerol are added. These acts as negative catalyst.