Thiamine (vitamin B1) deficiency diseases have a lower prevalence now than in the past. However, they are seen as beriberi in some developing regions and in regions of crisis, and as Wernicke–Korsakoff syndrome in some alcoholics. One type of beriberi causes neurological symptoms such as weakness, fatigue, and loss of sensation. What is a possible explanation for these symptoms? a. Thiamine is necessary for gluconeogenesis. b. Coenzymes of the pentose phosphate pathway require thiamine as a precursor. c. The metabolism of glucose provides most of the energy for the brain. In humans, d. thiamine must be obtained in the diet. Hexokinase requires thiamine.