A 9-year-old child in a developing country is brought to a clinic by his parents because he has trouble keeping up with his classmates on the playground. Physical examination is remarkable for pulmonary rales. Chest x-ray shows biventricular dilation of the hea. Deficiency of which of the following vitamins is the most likely cause of this child's condition?
Ascorbic acid Retinol Riboflavin Thiamine