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
DiGeorge's syndrome is due to 
Select and explain. 
A. Congenital thymic aplasia, B. Deficiency of complement factors, C. Inborn error of metabolism, D. Chromosomal anomaly
A: Congenital thymic aplasia
Answer: A: Congenital thymic aplasia 
Explanation: None