In which type of polymerisation mechanism small molecules such as $H_2O,NH_3,HCl,ROH,.....$ are lost?

Question

$\begin{array}{1 1}(a)\;\text{Free radical addition polymerisation}\\(b)\; \text{Step growth polymerisation}\\(c)\;\text{Cationic polymerisation}\\(d)\;\text{Anionic polymerisation}\end{array}$