The number of bridging CO ligand(s) and Co-Co bond(s) in Co₂(CO)₈, respectively are :

The coordination number of Th in K₄[Th(C₂O₄)₄(OH₂)₂] is :
(C₂O$${_4^{2 - }}$$ = Oxalato)

Match the metals (column I) with the coordination compound(s)/enzyme(s) (column II)

(Column I) Metals		(Column II) Coordination compounds(s) enzyme(s)
(A)	Co	(i)	Wilkinson catalyst
(B)	Zn	(ii)	Chlorophyl
(C)	Rh	(iii)	Vitamin B12
(D)	Mg	(iv)	Carbonic anhydrase

A reaction of cobalt (III) chloride and ethylenediamine in a 1 : 2 mole ratio generates two isomeric products A (violet coloured) and B (green coloured). A can show optical activity, but B is optically inactive. What type of isomers does A and B represcent?