Which vitamin is essential for the conversion of homocysteine to methionine in the methionine cycle?

A Vitamin B6
B Vitamin B9 (Folic acid)
C Vitamin B12 ✓
D Vitamin C

Explanation

Vitamin B12, specifically methylcobalamin, acts as a coenzyme for methionine synthase, which converts homocysteine to methionine.

Source

Biochemistry textbooks and research articles
Vitamins Biochemistry Methionine Cycle and Homocysteine Metabolism Hard MEDICAL Confidence: high