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
Foetal pas can be detected by X-ray usually by : 
Select and explain. 
A. 8 weeks, B. 12 weeks, C. 14 weeks, D. 16 weeks
D: 16 weeks
Answer: D: 16 weeks 
Explanation: 16 weeks