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
Xanthoproteic reaction involves- 
Select and explain. 
A. Carbolic acid, B. H2SO4, C. HCL, D. Nitric acid
D: Nitric acid
Answer: D: Nitric acid 
Explanation: Xanthoproteic reaction is method for determination of amount of protein soluble in solution, using concentrated nitric acid.