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: Social & Preventive Medicine
Iodine deficient population in the world is: 
Select and explain. 
A. 20 million, B. 12 million, C. 9 million, D. 6 million
A: 20 million
Answer: A: 20 million 
Explanation: 20 million