Which of the following is correct about vitamin B12?

The correct answer is Option (4) → All of the above

Vitamin B₁₂ is cyanocobalamine, the anti-pernicious anaemia factor, and a coordination compound of cobalt, so all three statements are correct.

NCERT (2026-27 edition):
5.7 Importance and Applications of Coordination Compounds – “… Vitamin B₁₂, cyanocobalamine, the anti–pernicious anaemia factor, is a coordination compound of cobalt.”