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: Forensic Medicine
[{'content': 'Gestational sac can be seen using ultrasonography at the earliest by: Gujarat 07 \nSelect and explain. \nA. 3rd week, B. 4th week, C. 5th week, D. 8th week', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. 5th week', 'role': 'assistant'}]