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
Leukocyte alkaline phosphatase is elevated in: 
Select and explain. 
A. Pernicious anemia, B. Sickle cell anemia, C. Polycythemia vera, D. Plummer Vinson syndrome
C: Polycythemia vera
Answer: C: Polycythemia vera 
Explanation: None