Glycogen Storage Disease Type I

A 4-month-old male infant presents to the emergency department with recurrent hypoglycemia, lactic acidosis, hyperuricemia, hypertriglyceridemia, and massive hepatomegaly with a characteristic doll-like face. Liver biopsy shows glycogen accumulation and steatosis. Enzymatic assay confirms deficiency of glucose-6-phosphatase. Gene sequencing reveals biallelic pathogenic variants in G6PC on chromosome 17q21.31. Both parents are phenotypically normal but carrier-tested as heterozygous. The pedigree shows affected males and females, transmission from unaffected parents, and no male-to-male transmission. The inheritance pattern marked **A** in the diagram is most consistent with which of the following?