A man presents with difficulty walking and painful calves. He has a history of alcohol use disorder and ulcerative colitis, both untreated. He reports no history of chronic diarrhea. A blood tox screen is negative for alcohol and illicit drugs. His examination is significant for several neurologic findings: altered proprioception, distal numbness, hyporeflexia, confusion, and nystagmus. Perioral and tongue examination is normal. These symptoms are most likely related to a deficiency of which of the following vitamins?
AB1
BB2
CB3
DC
