This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ULTRASOUND, Subject name: Radiology
Gas shadow in hea and great vessels appears in- 
Select and explain. 
A. IUD, B. Aboion, C. Still bih, D. None
A: IUD
Answer: A: IUD 
Explanation: IUD ROBE SIGN: Hyperechoic area inside hea and umbilical vein because presence of AIR SPALDING SIGN: Overlapping sutural bones on USG SPALDING SIGN ROBE SIGN