An aqueous solution of metal ion `M_(1)` reacts separately with reagents Q and R in excess to give tetrahedral and square planar complexes, respectively. An aqueous solution of anotherr metal ion `M_(2)` always forms tetrahedral complex with these reagents. Aqueous solution of `M_(2)` on reaction with reagent S gives white precipitate which dissolves in excess of S. The reactions are summarized in the scheme given ahead.
SCHEME:
Tetrahedral `overset(Q)underset("excess")larr M_(1)overset(R)underset("excess")rarr` Square planar
`{:("Tetrahedral"overset(Q)underset("excess")larrM_(2)overset(R)underset("excess")rarr"Tetrahedral"),(" "darrS."stoichiometric amount"),(" ""White ppt" overset(S)underset("excess")rarr."Precipitate dissolves"):}`
`M_(1),Q` and R, respectively are:
A. `Zn^(2+),KCN` and `HCI`
B. `Ni^(2+),HCI` and KCN
C. `Cd^(2+),KCN` and HCI
D. `Co^(2+),HCI` and KCN
