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: Physiology
[{'content': 'In a DNA molecule adenine always forms a linkage with \nSelect and explain. \nA. Guanine, B. Cytosine, C. Thymine, D. Uracil', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]