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: Medicine
The commonest cause of congenital hypothyroidism- 
Select and explain. 
A. Thyroid dysgenesis, B. Pendred syndrome, C. Defective release, D. Deficiency of deiodinase
A: Thyroid dysgenesis
Answer: A: Thyroid dysgenesis 
Explanation: None