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
Method (s) to determine protein structure is/are 
Select and explain. 
A. X-Ray Crystallography, B. NMR Spectroscopy, C. Infrared spectroscopy, D. All of these
D: All of these
Answer: D: All of these 
Explanation: X-ray crystallography (X-ray diffraction)
UV light spectroscopy and infra-red spectroscopy
Nuclear magnetic resonance (NMR) spectroscopy
Polychromatic X-ray crystallography (Laue diffraction)  
Optical rotatory dispersion
Circular dichroism
Computer-based modelling
Mass spectrometry