This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
[{'content': 'Regarding severe combined immunodeficiency, which is true? \nSelect and explain. \nA. Adenosine deaminase deficiency, B. Decreased circulating lymphocytes, C. NADPH oxidase deficiency, D. C1 esterase deficiency', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Severe combined immunodeficiency Constellation of genetically distinct syndromes Defects in both humoral & cell-mediated immune response MC form - XLR - so more in males; mutation in g chain subunit of cytokine receptors Remaining - AR; deficiency of enzyme ADA', 'role': 'assistant'}]