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
The definitive sign of pregnancy is : 
Select and explain. 
A. HCG estimation, B. Quickening, C. Chadwick sign, D. Fetal skeleton in X-rays
D: Fetal skeleton in X-rays
Answer: D: Fetal skeleton in X-rays 
Explanation: Fetal skeleton in X-rays