Aqueous solution of nickel sulphate on treating with pyridine and then adding a solution of sodium nitrite gives dark blue crystals of
A. ` [Ni (py)_4]SO_(4)`
B. `[Ni(py)_(2)(NO_(2))_(2)]`
C. `[Ni(py)_(4)](NO_(2))_(2)`
D. `[Ni(py)_(3)(NO_(2))]_(2)SO_(4)`
