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: Physiology
Hemophilia B is deficiency of which factor: September 2007 
Select and explain. 
A. IX, B. XII, C. VIII, D. X
A: IX
Answer: A: IX 
Explanation: Ans. A: IX Hemophilia B is also known as Christmas disease. Hemophilia A is deficiency of factor VIII (classical hemophilia).It has sex-linked inheritance.