This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Primary Immunodeficiency, Subject name: Pediatrics
[{'content': 'True about SCID in children is: \nSelect and explain. \nA. It is due to adenosine deaminase deficiency, B. Humoral immunity is predominantly affected, C. Child should receive double dose of all vaccines, D. Patients with SCID have normal thymus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: SCID: It is due to adenosine deaminase deficiency SCID- combined antibody and cellular defect Live vaccines are contraindicated in SCID Patients with SCID have very small thymus; tonsils & adenoids are also absent or underdeveloped', 'role': 'assistant'}]