This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Development period- week 1,2,3,4, Subject name: Anatomy
[{'content': 'Hea beat in conceptus can be detected earliest by \nSelect and explain. \nA. 4-6 weeks, B. 12-14 weeks, C. 14-16 weeks, D. 21-24 weeks', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The CVS is the earliest system to become functional is human. Hea begins to beat in the fouh week of development( Day 22 ).', 'role': 'assistant'}]