$\begin {array} {1 1} (a)\;\text{It involves free radical addition}\\ (b)\;\text{The presence of carbon tetrachloride in styrene polymerisation results in lowering of average molecular mass of the polymer} \\ (c)\;\text{The presence of benzoquinone increases the polymerisation process}\\ (d)\;\text{The presence of $CCl_4$ acts as inhibitor} \end {array}$
