$\begin{array}{1 1} \text{(a) (i)Because bond dissociation enthalpy of H-Cl is lower than HF.(ii) White phosphorus is more reactive than red phosphorus due to discrete tetrahedral structure and angular strain} \\ \text{(b) (i)Because bond dissociation enthalpy of H-Cl is higher than HF.(ii) White phosphorus is more reactive than red phosphorus due to discrete trigonal structure and angular strain} \\ \text{(c) (i)Because bond dissociation enthalpy of H-Cl is lower than HF.(ii) White phosphorus is more reactive than red phosphorus due to square planar structure and angular strain} \\\text{(d) (i)Because Ionization energy of H-Cl is lower than HF.(ii) White phosphorus is more reactive than red phosphorus due to discrete tetrahedral structure and angular strain} \end{array} $