Explanation

(b)
No, of hybrid orbital $= \frac{1}{2}\lbrack$No.of$\ e^{-}\$in$\$V-shell of atom$\ + \$No.of monovalent atoms –charge on cation +charge on anion]
No. of hybrid orbital 2 3 4 5 6 7
Type of hybridisation $sp$ $sp^{2}$ $sp^{3}$ $sp^{3}d$ $sp^{3}d^{2}$ $sp^{3}d^{3}$
Hybridisation in $TeCl_{4}$ :
No. of hybrid orbital $= \frac{1}{2}\lbrack 6 + 4 + 0 + 0\rbrack = \ 5$
Hence, $TeCl_{4}$ shows $sp^{3}d$ hybridisation.