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
[{'content': 'True about DNA structure: \nSelect and explain. \nA. Purines are adenne and guanine & pyrimidines are uracil and cytosine, B. Watson and Crick discovered structure in 1973, C. Deoxyribose-phosphate backbone with bases stacked inside, D. Mainly consists of left handed helix', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Deoxyribose-phosphate backbone with bases stacked inside', 'role': 'assistant'}]