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: Gynaecology & Obstetrics
Fetal hea can be detected earliest with trans-vaginal sonography at (from the last menstrual period) : 
Select and explain. 
A. 35 days, B. 38 days, C. 53 days, D. 46 days
D: 46 days
Answer: D: 46 days 
Explanation: 46 days