Correct Answer – B
Group 9 elements are cobalt, rhodium, iridium and Meitnerium. Cobalt is a bluish white, hard metal, and like Fe, it is a magnetic (ferromagnetic) material but, is appueous states, is a strong oxidising agent, it can oxidise even water with the evolution oxygen. Vitamin `B_(12)` has `Co(+3)` at the core of the molecule, surrounded by a ring structure similar to the porphyrin ring. Injections of this vitamin are used in the treatment of pernicious anemia. Cobalt is also involved in some enzyme functioning. `Co(+3)` exhibits unique tendency of forming a large number of coordination complexes especially with N-donor ligands. Cobalt compounds find use in ceramic and paint industries and as cataysts.