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: Radiology
[{'content': 'USG can detect gestation sac earliest at: \nSelect and explain. \nA. 5-6 weeks of gestation, B. 7-8 weeks of gestation, C. 10 weeks of gestation, D. 12 weeks of gestation', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. 5-6 weeks of gestation', 'role': 'assistant'}]