This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
[{'content': "DiGeorge's syndrome is due to \nSelect and explain. \nA. Congenital thymic aplasia, B. Deficiency of complement factors, C. Inborn error of metabolism, D. Chromosomal anomaly", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]