This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Health care of community & international health, Subject name: Social & Preventive Medicine
Recommended number of population per PHC in tribal area 
Select and explain. 
A. 30000, B. 20000, C. 40000, D. 25000
B: 20000
Answer: B: 20000 
Explanation: Ref:Park's Textbook of Preventive and Social Medicine 25th Ed