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: Biochemistry
Which of the following assays are used to estimate amount of glycated Hemoglobin? 
Select and explain. 
A. HPLC, B. Immunoassay, C. Affinity chromatography, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: All the 3 assays can be used to estimate amount of glycated hemoglobin.
Normal level of HbA1C is < 5.5%.
High performance liquid chromatography employs cation exchange chromatography.