<prompt> 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 childs condition?Ascorbic acidRetinolRiboflavinThiamine  <response>: Thiamine deficiency is most frequently encountered in alcoholics and in developing countries. Deficiency of this vitamin can take several forms: dilated cardiomyopathy, polyneuropathy and mamillary body degeneration Wernicke-Korsakoff syndrome. Ascorbic acid Vitamin C deficiency causes scurvy, associated with capillary fragility, bony abnormalities, and poor wound healing. Retinol Vitamin A deficiency causes blindness and impaired immune responses. Riboflavin deficiency causes cheilosis, glossitis, and dermatitis. Ref: Bender D.A. 2011. Chapter 44. Micronutrients: Vitamins Minerals. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell Eds,Harpers Illustrated Biochemistry, 29e. 