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
Flaer assay is used for 
Select and explain. 
A. Hereditary spherocytosis, B. Thalassemia, C. Paroxysmal nocturnal hemoglobinuria, D. All of the above
C: Paroxysmal nocturnal hemoglobinuria
Answer: C: Paroxysmal nocturnal hemoglobinuria 
Explanation: Flaer (Flourescein - Labelled proaerolysin) is sensitive test for PNH.