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
Best modality to diagnose unruptured tubal pregnancy is : 
Select and explain. 
A. Vaginal ultrasound, B. Serum hCG estimation, C. Serum Progesterone estimation, D. Culdocentesis
A: Vaginal ultrasound
Answer: A: Vaginal ultrasound 
Explanation: Vaginal ultrasound