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': 'If a completely radioactive double stranded DNA molecule undergoes two rounds of replication in a solution free of radioactive label. What is the radioactivity status of the resulting four double stranded DNA molecules \nSelect and explain. \nA. 50% of the DNA molecules have no radioactivity, B. 2 DNA molecules have radioactivity in both strands, C. I DNA molecule has radioactivity in both strands, D. All 4 DNA molecules have radioactivity', 'role': 'user'}, {'content': 'Answer: A \nExplanation: DNA replication is semi conservative. Thus 2 DNA molecules have one strand with radioactivity and other 2 DNA molecules have no radioactivity.', 'role': 'assistant'}]