Step 1: PCl₅ की geometry।
$ sp^3d $ hybridization, 5 bond pairs, 0 lone pairs: Trigonal bipyramidal (III)।
Step 2: BrF₅ की geometry।
Br: 7 valence e, 5 bonds + 1 lone pair: $ sp^3d^2 $: Square pyramidal (IV)।
Step 3: BF₄⁻ की geometry।
$ sp^3 $, 4 bond pairs, 0 lone pairs: Tetrahedral (I)।
Step 4: $ [Ni(CN)_4]^{2-} $ की geometry।
$ Ni^{2+} $: $ 3d^8 $, $ CN^- $ strong field: $ dsp^2 $: Square planar (II)।
Step 5: मिलान।
A-III, B-IV, C-I, D-II।
Step 6: उत्तर।
\[ \boxed{A\text{-III},\; B\text{-IV},\; C\text{-I},\; D\text{-II}} \]