Explanation

(b)
In $XeF_{5}^{+}$, $Xe$ atom has only seven electrons, $ie,\ 5s^{2}\ 5p^{5}$. Here, two $5p$ electrons are promoted to $5d$ sub level. Then $5s$, three $5p$ and two $5d$ orbitals hybridize to give six $sp^{3}d^{2}$ hybrid orbitals in an octahedral geometry. Out of these, five orbitals are singly occupied which form sigma bonds with five F atoms. The sixth hybrid orbital is occupied by a lone pair in $trans$ position giving a square pyramidal structure