Q. A 1-year-old boy is brought to the pediatrician by his parents, who are concerned about his health. Each time they have introduced fruits to his diet, he experiences vomiting, and they have noticed he becomes lethargic and unusually tired. Physical examination reveals hepatomegaly. Lab tests show hypoglycemia, lactic acidosis, and the presence of reducing substances in both his serum and urine. What is the most likely diagnosis for this patient?