This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ULTRASOUND, Subject name: Radiology
[{'content': 'Fetal cardiac activity can be detected earliest by USG at which age of Intrauterine life- \nSelect and explain. \nA. 1-2 week, B. 2-4 week, C. 5-6 week, D. 6-8 week', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Fetal cardiac activity can be detected earliest by USG at 5-6-week age of intrauterine life.', 'role': 'assistant'}]