Step 1: Concept
Vitamins function as essential coenzymes or precursors to coenzymes in various metabolic reactions.
Step 2: Meaning
Each B-vitamin has a specific chemical role, such as transferring groups or facilitating redox reactions.
Step 3: Analysis
Vitamin B1 (Thiamine) is involved in carbonyl (aldehyde) group transfer (A-I). Vitamin B12 (Cobalamin) is essential for alkylation and methyl group transfer (B-IV). Vitamin B2 (Riboflavin) forms FAD/FMN for oxidation-reduction reactions (C-III). Vitamin B6 (Pyridoxine) is the primary coenzyme for amino group transfer (transamination) (D-II).
Step 4: Conclusion
The correct matching is A-I, B-IV, C-III, D-II.
Final Answer: (D)