The non-existence of $\mathrm{PbI}_{4}$ and $\mathrm{PbBr}_{4}$ is due to
The non-existence of $\mathrm{PbI}_{4}$ and $\mathrm{PbBr}_{4}$ is due to
highly oxidising nature of $\mathrm{Pb}^{4+}$ ions
highly reducing nature of $I^{-}$ and $\mathrm{Br}^{-}$ ions
larger size of $\mathrm{Pb}^{4+}, \mathrm{Br}^{-}$ and $\mathrm{I}^{-}$ions
Both (a) and (b)
Solution
The non-existence of $\mathrm{PbI}_{4}$ and $\mathrm{PbBr}_{4}$ is probably due to the strong oxidising power of $\mathrm{Pb}^{4+}$ ions and strong reducing power of $\mathrm{I}$ and $\mathrm{Br}^{-}$ions.