$N_2$ forms $Ncl_3$ whereas P can form both $Pcl_3$ and $PCl_5$ why ?

Question

$(a)\;\text{P has low lying 3d orbitals, which can be used for bonding but N does not have low lying 3d orditals.} \\ (b)\;\text{N atom is larger than P in size.} \\(c)\;\text{P is more reactive towards Cl than} \\(d)\;\text{none of these}$