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
Protein purification and separation can be done by all, EXCEPT: 
Select and explain. 
A. Chromatography, B. Dialysis, C. Electrophoresis, D. Densitometry
D: Densitometry
Answer: D: Densitometry 
Explanation: Densitometry is the procedure which is used to measure the quantity of the protein. Protein purification and separation can be done by the following methods: Chromatography Dialysis Electrophoresis Centrifugation Precipitation