Question: Which of the following is a function of vitamin B12?

A: Synthesis of TMP (thymidine monophosphate)
B: Decarboxylation of amino acids to form amine neurotransmitters
C: Synthesis of methionine from homocysteine
D: Carboxylation of pyruvate to oxaloacetate
Please eliminate two incorrect options first, then think it step by step and choose the most proper one option.