This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Bio-Chemistry), Subject name: Biochemistry
[{'content': 'Watson Crick model of DNA was proposed on the basis of \nSelect and explain. \nA. X-ray crystallography, B. Chromatography, C. Gel electrophoresis, D. X-ray diffraction studies', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (A) X-ray crystallography> X-ray crystallography theoretically offered the opportunity to reveal the molecular structure of large molecules like proteins and DNA, but there were serious technical problems then preventing X-ray crystallography from being applicable to such large molecules.', 'role': 'assistant'}]