B. A (4) B (3) C (2) D (1)

C. A (5) B (1) C (4) D (2)

D. A (4) B (1) C (2) D (3)

The correct answer will be the option (iii) A (5) B (1) C (4) D (2)

Hence, matching the two columns the right combination will be:

A. [Co(NCS)(NH₃)₅](SO₃) -5. + 3 (oxidation no.of Co, x =-1(-1)-(-2)=+3)

B. [Co(NH₃)₄Cl₂]SO₄ -1. + 4 (oxidation no. Of Co, x =-2x(-2)-1(-2)=+4)

C. Na₄[Co(S₂O₃)₃] -4.+ 2 (oxidation no. Of Co, x=-3(-2) – 4x(+1)=+2 )

D. [Co₂(CO)₈] –2. 0 . (as CO is a neutral ligand, therefore Co here has a zero oxidation state)