A nurse is explaining the difference between Type 1 and Type 2 diabetes mellitus. Which statement accurately describes the cause of Type 1 diabetes mellitus?

Type 1 diabetes mellitus is a chronic metabolic disorder resulting from T-cell mediated autoimmune destruction of pancreatic beta cells within the islets of Langerhans. This absolute insulin deficiency impairs peripheral glucose uptake and causes uninhibited hepatic gluconeogenesis. The metabolic deficit precipitates profound hyperglycemia and triggers ketogenesis without exogenous hormone replacement. A. Autoimmune destruction of beta cells: Environmental triggers induce selective immunological destruction of insulin-secreting tissue in genetically susceptible individuals. This progressive loss eliminates endogenous insulin synthesis, driving reliance on exogenous insulin replacement to prevent diabetic ketoacidosis. It represents the primary, definitive etiology of this specific metabolic disease. B. Insulin resistance: Decreased tissue sensitivity to circulating insulin characterizes the metabolic profile of type 2 diabetes rather than type 1 pathology. Defective intracellular signaling cascades diminish insulin receptor responsiveness in skeletal muscle, liver, and adipose tissues. This mechanism coexists with relative, rather than absolute, pancreatic secretory deficiencies. C. Poor diet: Excessive caloric intake and glycemic loads contribute heavily to metabolic syndrome and peripheral insulin receptor downregulation over time. Nutrient choices influence lifestyle-related metabolic disorders but do not initiate the specific autoimmune cascades targeting pancreatic tissue. Nutritional habits are non-causal for primary type 1 pathogenesis. D. Obesity: Elevated body mass index drives systemic low-grade inflammation and ectopic lipid accumulation, accelerating peripheral tissue resistance to insulin. While strongly associated with type 2 disease mechanics, adiposity does not trigger the autoantibody production seen in type 1 individuals. It remains an independent variable in autoimmune pancreatic destruction.