A cofactor is a non-protein chemical compound or metallic ion which is required for the brisk activity of the enzyme. Vitamins acts as a precursor for many organic cofactors like vitamins B1, B2, B6, B12, niacin, folic acid) or as coenzymes themselves.

Vitamin serves the function of a coenzyme.

Coenzymes are small molecules that work in conjunction with enzymes to facilitate various biochemical reactions in the body. They are essential for the proper functioning of enzymes, which are proteins that act as catalysts in chemical reactions.

Vitamins are organic compounds that are required in small amounts for the normal functioning of the body. They play a crucial role in various metabolic processes and are often involved in enzymatic reactions. Many vitamins act as coenzymes, meaning they bind to enzymes and help catalyze specific reactions.

Here are some key points to explain why the correct answer is option 'B':

1. Definition of coenzyme:
- A coenzyme is a non-protein compound that is required for the activity of an enzyme.
- Coenzymes often participate directly in the chemical reactions catalyzed by enzymes.

2. Role of coenzymes:
- Coenzymes assist enzymes in carrying out specific reactions by transferring chemical groups or electrons.
- They can act as carriers of chemical groups, such as hydrogen atoms, methyl groups, or acetyl groups.
- Coenzymes can also participate in redox reactions, transferring electrons between molecules.

3. Vitamin as a coenzyme:
- Many vitamins serve as coenzymes or precursors to coenzymes.
- For example, vitamin C acts as a coenzyme in the synthesis of collagen, a protein important for the structure of connective tissues.
- Vitamin B1 (thiamine) is a coenzyme in the metabolism of carbohydrates, while vitamin B2 (riboflavin) is a precursor to coenzymes involved in energy production.

4. Importance of vitamins as coenzymes:
- Without the necessary vitamins, the enzymes that rely on them as coenzymes cannot function properly.
- Deficiencies in specific vitamins can lead to deficiency diseases, where the lack of a particular coenzyme disrupts important metabolic pathways.

In conclusion, vitamins serve the function of coenzymes by binding to enzymes and assisting in various biochemical reactions. They are essential for the proper functioning of enzymes and play a crucial role in maintaining overall health and metabolism.