A-ii; B-i; C-iv; D-iii
A-iii; B-iv; C-i; D-ii
A-iv; B-iii; C-i; D-ii
A-i; B-ii; C-iii; D-iv
(i) Wilkinson catalyst : RhCl(PPh3)3
(ii) Chlorophyll : C55H72O5N4Mg
(iii) Vitamin B12 (also known as cyanocobalamin) contains cobalt
(iv) Carbonic anhydrase contains a zinc ion.