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': 'The base not present in DNA is: \nSelect and explain. \nA. Adenine, B. Uracil, C. Guanine, D. Thymine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Uracil', 'role': 'assistant'}]